You can't switch app stores will nilly just because.
You will need a valid payment method from the new region to complete the switch.
If you have balance from the current region, you will need to spend it. If you cannot spend it because it's not enough for a single item, then you either need to add a payment method from your current region and buy something more expensive than your balance or contact Apple Support directly and have them remove it.
click here ➜ contact Apple Support
Also note, that to chang your region you will need to cancel any active subscriptions you may have and wait for them to expire.
For more details about changing the Apple Store region, see the following support document.
click here ➜ Change your Apple Account country or region - Apple Support