To view your Return Policy or create a new one, please go to this Settings Page in your Etsy Seller account.
If you do not have one, please create it and link it to at least one active listing in your Etsy Shop.
As shown in the screenshot, you should see something similar on your end; for example, 2 active listings use this policy.
Enter that number into your Etsy field mapping in your Shoppingfeed account.
Note: If the Return Policy you wish to use has no active listings on Etsy, the number will be 0, and you will be unable to open a link. If this is the case, you will need to manually assign at least one product to this template in your Etsy account itself, and then you will be able to get the URL with the Template ID number in it, using the above method.