removing my store credit

Depending on the amount, 

See -> Check your Apple ID balance

Check your Apple ID balance – Apple Support (UK)

• If your balance is less than the cost of a single item, contact Apple Support.

• scroll to ⤵️

If you have Apple ID balance you can't use.

You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards or unused Apple ID balance for cash, except as required by law. If your jurisdiction allows the 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 delivery address.

There are 2 ways to remove your store credit.

Spend it, or let it be on your account. You cannot move App Store credit to your bank account or something