Some Shopify apps use xml or xlsx file to import/export data. Awful lot of them need product id to identify the item in your online store. These steps will help you to find this number.
Step 1. Find related product
To get the Shopify Product ID Number go to “Products”.
Step 2. Open the product page
Click on the title that you want to get the Product ID Number for.
Step 3. Look at url of the product
Go to the URL at the top and copy the number that comes after “…/products/”
It is the Shopify Product ID number which is unique for every item in your online store.