You will find your product template in the Templates, Sections or Snippets folder.

You're looking for the file that contains the markup that displays the price on the product page.

The name of this file varies per theme. Some themes use "product-template.liquid" or "product.liquid" others have different names.

Search the file (use CTRL+F when inside the code panel) for the following text:
.price | money

You should find one or more blocks of markup that look similar to this:
{{ product.price | money }}
note that product could have a different name such as current_variant.

Copy the content of the template before you make any changes. Create a separate file and paste the content. Repeat for every file you plan to change. Better safe than sorry!