WordPress uses a template system- content is stored in a database and gets inserted into a template when a page is served, so pages and products don’t exist as separate, physical things.
To edit the templates Wp E-Commerce uses, go to Settings > Store and click on the presentation tab. There will be an advanced Theme Settings box which will allow you to select which templates you want to move into your active theme directory. Once you’ve moved them you can then edit those templates without losing changes in a plugin update.
Note that, much like WordPress posts and pages, your single product pages all share the same template, so you’ll need some additional code in your template to determine what the current product is if you want to style specific products differently than others.