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I created a new function call getAllGroups,

cheers

You should do an override of AdminOrdersController.php

<?php
/**
 * 2007-2018 PrestaShop.
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * https://opensource.org/licenses/OSL-3.0
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to [email protected] so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade PrestaShop to newer
 * versions in the future. If you wish to customize PrestaShop for your
 * needs please refer to http://www.prestashop.com for more information.
 *
 * @author    PrestaShop SA <[email protected]>
 * @copyright 2007-2018 PrestaShop SA
 * @license   https://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
 * International Registered Trademark & Property of PrestaShop SA
 */

/**
 * @property Order $object
 */
class AdminOrdersController extends AdminOrdersControllerCore
{

    public function __construct()
    {
        $this->bootstrap = true;
        $this->table = 'order';
        $this->className = 'Order';
        $this->lang = false;
        $this->addRowAction('view');
        $this->explicitSelect = true;
        $this->allow_export = true;
        $this->deleted = false;

        parent::__construct();

        $this->_select = '
        a.id_currency,

        c.id_customer,



        a.id_order AS id_pdf,
        CONCAT(LEFT(c.`firstname`, 1), \'. \', c.`lastname`) AS `customer`,
        osl.`name` AS `osname`,
        os.`color`,
        IF((SELECT so.id_order FROM `' . _DB_PREFIX_ . 'orders` so WHERE so.id_customer = a.id_customer AND so.id_order < a.id_order LIMIT 1) > 0, 0, 1) as new,
        country_lang.name as cname,
        IF(a.valid, 1, 0) badge_success';

        $this->_join = '
        LEFT JOIN `' . _DB_PREFIX_ . 'customer` c ON (c.`id_customer` = a.`id_customer`)
        INNER JOIN `' . _DB_PREFIX_ . 'address` address ON address.id_address = a.id_address_delivery
        INNER JOIN `' . _DB_PREFIX_ . 'country` country ON address.id_country = country.id_country
        INNER JOIN `' . _DB_PREFIX_ . 'country_lang` country_lang ON (country.`id_country` = country_lang.`id_country` AND country_lang.`id_lang` = ' . (int) $this->context->language->id . ')
        LEFT JOIN `' . _DB_PREFIX_ . 'order_state` os ON (os.`id_order_state` = a.`current_state`)
        LEFT JOIN `' . _DB_PREFIX_ . 'order_state_lang` osl ON (os.`id_order_state` = osl.`id_order_state` AND osl.`id_lang` = ' . (int) $this->context->language->id . ')';
        $this->_orderBy = 'id_order';
        $this->_orderWay = 'DESC';
        $this->_use_found_rows = true;

        $statuses = OrderState::getOrderStates((int) $this->context->language->id);
        foreach ($statuses as $status) {
            $this->statuses_array[$status['id_order_state']] = $status['name'];
        }

        $this->fields_list = array(
            'id_order' => array(
                'title' => $this->trans('ID', array(), 'Admin.Global'),
                'align' => 'text-center',
                'class' => 'fixed-width-xs',
            ),

            /*Modif*/

            'id_customer' => array(
                'title' => $this->trans('Groups', array(), 'Admin.Global'),
                'callback' => 'getAllGroups',
            ),

            /*Modif*/


            'reference' => array(
                'title' => $this->trans('Reference', array(), 'Admin.Global'),
            ),
            'new' => array(
                'title' => $this->trans('New client', array(), 'Admin.Orderscustomers.Feature'),
                'align' => 'text-center',
                'type' => 'bool',
                'tmpTableFilter' => true,
                'orderby' => false,
            ),
            'customer' => array(
                'title' => $this->trans('Customer', array(), 'Admin.Global'),
                'havingFilter' => true,
            ),
        );

        if (Configuration::get('PS_B2B_ENABLE')) {
            $this->fields_list = array_merge($this->fields_list, array(
                'company' => array(
                    'title' => $this->trans('Company', array(), 'Admin.Global'),
                    'filter_key' => 'c!company',
                ),
            ));
        }

        $this->fields_list = array_merge($this->fields_list, array(
            'total_paid_tax_incl' => array(
                'title' => $this->trans('Total', array(), 'Admin.Global'),
                'align' => 'text-right',
                'type' => 'price',
                'currency' => true,
                'callback' => 'setOrderCurrency',
                'badge_success' => true,
            ),
            'payment' => array(
                'title' => $this->trans('Payment', array(), 'Admin.Global'),
            ),
            'osname' => array(
                'title' => $this->trans('Status', array(), 'Admin.Global'),
                'type' => 'select',
                'color' => 'color',
                'list' => $this->statuses_array,
                'filter_key' => 'os!id_order_state',
                'filter_type' => 'int',
                'order_key' => 'osname',
            ),
            'date_add' => array(
                'title' => $this->trans('Date', array(), 'Admin.Global'),
                'align' => 'text-right',
                'type' => 'datetime',
                'filter_key' => 'a!date_add',
            ),
            'id_pdf' => array(
                'title' => $this->trans('PDF', array(), 'Admin.Global'),
                'align' => 'text-center',
                'callback' => 'printPDFIcons',
                'orderby' => false,
                'search' => false,
                'remove_onclick' => true,
            ),
        ));

        if (Country::isCurrentlyUsed('country', true)) {
            $result = Db::getInstance(_PS_USE_SQL_SLAVE_)->executeS('
               SELECT DISTINCT c.id_country, cl.`name`
               FROM `' . _DB_PREFIX_ . 'orders` o
               ' . Shop::addSqlAssociation('orders', 'o') . '
               INNER JOIN `' . _DB_PREFIX_ . 'address` a ON a.id_address = o.id_address_delivery
               INNER JOIN `' . _DB_PREFIX_ . 'country` c ON a.id_country = c.id_country
               INNER JOIN `' . _DB_PREFIX_ . 'country_lang` cl ON (c.`id_country` = cl.`id_country` AND cl.`id_lang` = ' . (int) $this->context->language->id . ')
               ORDER BY cl.name ASC');

            $country_array = array();
            foreach ($result as $row) {
                $country_array[$row['id_country']] = $row['name'];
            }

            $part1 = array_slice($this->fields_list, 0, 3);
            $part2 = array_slice($this->fields_list, 3);
            $part1['cname'] = array(
                'title' => $this->trans('Delivery', array(), 'Admin.Global'),
                'type' => 'select',
                'list' => $country_array,
                'filter_key' => 'country!id_country',
                'filter_type' => 'int',
                'order_key' => 'cname',
            );
            $this->fields_list = array_merge($part1, $part2);
        }

        $this->shopLinkType = 'shop';
        $this->shopShareDatas = Shop::SHARE_ORDER;

        if (Tools::isSubmit('id_order')) {
            // Save context (in order to apply cart rule)
            $order = new Order((int) Tools::getValue('id_order'));
            $this->context->cart = new Cart($order->id_cart);
            $this->context->customer = new Customer($order->id_customer);
        }

        $this->bulk_actions = array(
            'updateOrderStatus' => array('text' => $this->trans('Change Order Status', array(), 'Admin.Orderscustomers.Feature'), 'icon' => 'icon-refresh'),
        );
    }

    public static function getAllGroups($echo,$tr)
    {

        $customerGroups = Customer::getGroupsStatic((int)$echo);

        $group_name = [];

        foreach ($customerGroups as $id_group) {

            $group = new Group((int)$id_group,$this->context->language->id);
            $group_name[] .= $group->name;
            
        }

      
        return  implode(", ",$group_name);
    }

 
}