How do I change the country on my Store?

if you have any subscription or remaining itune balance , you cannot change region.

To Cancel subscription ,

1. Open the Settings app.
2. Tap your name.
3. Tap Subscriptions.
4. Tap the subscription.
5. Tap Cancel Subscription

if you have itune balance ,use them all or

if you can't use all of your balance contact Apple Support and ask them to clear your balance.

Try the following steps:

1) Go to settings

2)Click on your apple id on top

3) Go to media & purchases

4) Click view account

5) click on country and region and change the country