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i am running prestashop 1.7 and i have a need to HIDE price on $0 items or $0 combinations

i found this code but i have no idea what folder or file to edit or where or how to insert it ?

{if $product.price_amount eq "0"} 
<p> </p>
{else}
{block name='product_prices'}
   {include file='catalog/_partials/product-prices.tpl'}
{/block}
{/if}

you see i have combinations attribute's for a product and i have create some attribute tags like " select preferred " and i have set them to "0" so people dont order but the price still shows? $0.00 need some help please if you wouldn't mind 

bottom line i just need so that any product or combination that is set to $0.00 well automatically hide price.

any help would be greatly apricated GOD BLESS YOU AND HAPPY HOLIDAYS ! 

best,

Riot @GRFFX 

help needed how to hide price on $0 price " and EXACTLY WHERE TO PASTE CODE? " Presta Shop 1.7

i found this code but it does not work 

{if $product.price_amount eq "0"} 
<p> </p>
{else}
{block name='product_prices'}
   {include file='catalog/_partials/product-prices.tpl'}
{/block}
{/if}

???????

and HAVE NO CLUE WHAT FOLDER OR FILE TO EDIT I HAVE A CUSTOM THEME on shared hosting