[PS1.6] Multiply minimum quantity on product page add button

[stanleyek18]

Hello,

 

I'm trying to get multiply action on product add button - still, hours of searching without any success :-(
For example:

minimum product quantity - 3
when customer hits plus button he adds that value (3) and so on.

 

I'm very weak in js. In another shop I was able to that very quickly but sadly presta is too complicated. And this is a major thing for me.

 

Can you help me?