On the dashboard sidebar, click on Shop then click onto the product you need the ID for.
Scroll to the bottom of the product config page and you'll see the Product ID is noted at the bottom.
Finding the "standard in-store product ID"
Your account also has a built-in "in-store" product for any gift cards you sell in your venues.
This is often referred to as a "standard in-store product ID" if you're setting up an integration, such as with your EPOS.
If you need this you can find it on the In-Store Gift product, like shown below:
