Finding product ID
Product ID is also referred to as an ASIN. You can find the ASIN for a product on the Amazon retail web site, as part of the product detail page. You can simply go to the product detail page and find the ASIN in the Product Details section.
Alternatively you can find the ASIN in the URL of the product page.
Some products come in multiple variations, such as size or color. Variations have a parent-child relationship. The main product is the parent, with each unique variation a child. Both the parent and each child have their own unique ASIN. If you would like to retrieve information for a specific variation, you can simply use that variation's ASIN. Generally, it's best to use the ASIN for the main product. If the variations are priced differently, then a price range is returned.