How do I edit one entry of a table

I have a table named ‘Cart’ that stores quantity, product name, email. I want to edit just the ‘quantity’ if an entry with same email and product name exists in the table. How do I do it?
When I use the ‘Make changes to a thing’, ‘Cart’ is not present in the list of things [image attached for reference].

The RG is set to product, not to cart. So you can edit the current Product.
Do your product have a referenced field to cart? If yes, use Current cell Product’s cart
If Cart have a ref to product, you need to Do a Search for thing, where field “product” = Current cell product. : first item.

But actually, I think that the design of your Data may not be correct and may need some rethinking