Not sure what you're trying to ask here, but two things come to mind.
ETA: If you're asking where the eBay redemption code is, it's a 13-digit number that's emailed to you by Target ("delivery") with the subject "An eCard from Target. com." In the email, click on the button that takes you to eCard Center, enter your email address, click Print/View, and your code is the number under "Virtual Gift Card ID." If you ordered several cards in one order, you may have to scroll down the email to view each card.
When you use an eBay card in a transaction, it is forever linked to your eBay account and cannot be used by another account. Unfortunately, the eBay website doesn't have an easy feature, like Target's, that remembers your cards and remaining balance that you can select and apply. I believe the eBay native app (at least for iOS) does remember your previously used cards and gives you a box to click and apply the remaining balance. But since I shop through Ebates to get the 1% cash back for gift cards on eBay, I'm always using the full website.
A lot of us here like to keep track of gift card numbers on a spreadsheet so you can quickly refer to it to see which cards have been used, and which cards still have a balance.
I always mark the GC number as well as the balance. When you apply the GC and not all of it needs to be used, sometimes you think it will take money from one and it won't, so I always make sure to check the balances when I'm checking out and note that on the spreadsheet.
