i want to empty my apple store credit

Extracted from this article:--> Change your Apple ID country or region

Section: "What to do before you change your country or region"

• Spend any balance remaining on your Apple ID. If you're not sure whether you have a balance, check your Apple Account balance.

and

Section: "If you can't change your country or region"

• ....
• If you're a part of a Family Sharing group, you might not be able to change your country or region. Learn how to leave a Family Sharing group.
• If you still can't change your country or region, or you have less store credit than the cost of a single item, contact Apple Support.

Then contact Apple Support directly, using the above specific link.

Regards

Giulio