i'm working with joomla and virtuemart component

button in virtueMart don't have value :

<input type="button" class="quantity-controls quantity-plus">

actually i want to add : value="+" in button
but i have a problem . when i click inspect on browser , i can't find path address for code in my host

how can i find address for code ?

I'm not familiar with Joomla, but I suspect that the button has been dynamically generated by the Joomla app, and you need to be at least somewhat experienced in PHP in order to investigate this, unless it's easily found in one of their template files.