Agree on what Ryo said! When you are in the eform system you just click the “form 3” sheet as if you are going to complete them. After you pull up your transferor info you can skip the transferee page and go to the item page. When go to “add an item”. You will see a list of the item in your inventory.
As a FYI when something is missing and you try and correct it.. You make more head way bang your head against the wall. I had a missing pre- may gun that can in on a eform form. When I talked to the ATF on the phone they said it was in my inventory but no one could add it to my inventory. Eventually had to file a paper form 3 to transfer.
Hope this helps!