itunes gift card

• You can't check the remaining balance on an App Store & iTunes Gift Card. But you can check your Apple ID balance. Your Apple ID balance includes the balance from any App Store & iTunes Gift Cards that you have redeemed.

When you redeem an App Store & iTunes Gift Card, you can make purchases with your Apple ID balance, including apps, games, iCloud storage, subscriptions like Apple Music, and more. But for some purchases, Apple ID balance can't be used. Learn what you can buy with your Apple ID balance.

Source and more information at Redeem your App Store & iTunes Gift Card - Apple Support

I think Apple’s wording in the support article that Ijustwanttolookattheforums referenced is a little confusing. Once you redeem the gift card there is no balance on the card. The balance is in your Apple ID. Apple should just come out and say that rather than saying you can’t check the balance on the card. Just use the link posted above to check your Apple ID balance.

When you redeem an iTunes gift card and you have money in your Apple ID balance, you don’t have to do anything to pay for iCloud storage. The balance in your Apple ID will always be used for purchases before Apple takes the money from your debit or credit card. I pay for our iCloud family storage with iTunes gift cards every month. I never use my debit card.