Empty Apple Store

You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards, or unused Apple Account balance for cash, except as required by law. If your jurisdiction allows for refund of redeemed gift balances, you can contact Apple Support to request a refund. When you contact Apple, include the following information:

• Your Apple ID.
• The refund amount.
• Your current shipping address.

See Check your Apple Account balance - Apple Support.

Either spend it, or when your balance is less then the cost of a single item, please Contact - Official Apple Support to get help emptying your store credit