Changing up_quantity and down_quantity button on cart page

[Qcwng]

Hello,

I'am  very new in prestashop and i want to customize my cart page.

What i want is to change this input with up and down icon to add and minus icon and put them to the left and right side of the input. 

You can see what i want to render with attach image.

If i do understand, i need to change something in the theme.js file ? 

thanks in advance.