What Product markup can show in Google
With Product markup, Google can show the price, whether it's in stock, and the star rating right in your search result, and use the product in shopping results. Google needs the product name and at least one of: an offer (price), a review or an aggregate rating. For shopping features it also wants an image, the price and the currency.
Write the price as a plain number like 79.99, with no currency sign or commas, and set the currency as a three-letter code like USD.
Ratings must be real
Only add a rating and review count if real customer reviews are shown on the page. Google ignores, and can penalize, ratings that people can't see. Leave those two fields empty if you don't show reviews.
Shopify, WooCommerce and other stores
Most store themes already add Product markup. Check a product page with the free schema markup checker before adding more, so you don't end up with two conflicting copies.