The bundle must have its own standard product identifier. The identifier of any individual product in the bundle may not serve as the identifier for the bundle. You are responsible for obtaining a UPC for each bundle you create.
If the bundle does not have its own standard product identifier, you need to apply the UPC exemption. See How to list products that do not have a GTIN (UPC, EAN, JAN, or ISBN) .
In case you are selling the same item in a set of two or more using product identifier for items sold separately, enter the item package/set quantity (item-package-quantity). See Item Package Quantity (IPQ) for buldled products.