how to check balance of card

Pigkisser,

If the card was properly activated and has not yet been redeemed, it is worth the face value. Otherwise it is worth zero.

When you redeem an iTunes gift card, the full amount is immediately added to your account, and you can spend from the balance. Unlike some gift cards, there is not a running balance on the card.

If you already redeemed the cards and want to know the credit balance in your account, you can see it as follows: View your Apple ID balance - Apple Support