To empty your balance add an external payment method (e.g., a card) to buy an item (not a subscription) for more than your balance. The difference owed will be billed to your card, leaving nothing in your account.
- Payment types you can use —> https://support.apple.com/HT202631
- How to add a payment type —> https://support.apple.com/HT201266
Alternatively, ask Apple to remove and retain the balance.
- Click on the special empty-balance-request chat link at the bottom of this support article ➔ https://support.apple.com/119902#zerobalance
- General Apple support and service contact ➔ https://support.apple.com/106932 If live support options are available they will show near the bottom left. If numbers show as colored links, click on them for more options.
- With an iPhone, iPad, or Vision, you may be able to chat using the Apple Support App if it is available in your country ➔ https://apps.apple.com/app/apple-support/id1130498044
If you cannot contact Apple then the first method is the only way to empty your balance. If neither method works then you will have to create a new Apple Account when you are in the new country.
Additional changing account region support article ➔ https://support.apple.com/118283
Responses here come from Apple products users like yourself who cannot empty your account balance for you.