How to change country for App Store?

Click on the link and read how to "Change your Apple ID country or region" - https://support.apple.com/HT201389

Realize that doing the above is a fairly significant undertaking. You shouldn't do it just to get one app. You may also discover problems such as possibly requiring a valid for of payment from Australia.

???

Are you doing this on an iPhone (the forum to which you posted)? There is zero mention of iTunes.

On your iPhone, iPad, or iPod touch

1. Open the Settings app. 
2. Tap your name, then tap iTunes & App Store.
3. Tap your Apple ID, then tap View Apple ID. You might be asked to sign in.
4. 
   
5. Tap Country/Region.
6. 
   
7. 
8. Tap "Change Country or Region." If you don't see "Change Country or Region," contact Apple Support.
9. Tap your new country or region, then review the Terms & Conditions.
10. Tap Agree in the upper-right corner, then tap Agree again to confirm.
11. Select a payment method and enter your new payment information and
12. billing address, then tap Next. You must enter a valid payment method
13. for your new country or region.

On a computer it says open iTunes or the Music app.

On your computer

1. Open the Music app or iTunes.
2. In the menu bar at the top of the screen or the top of the iTunes window, click Account, then click View My Account. 
3. Sign in with your Apple ID, then click View Account.
4. On the Account Information page, click "Change Country or Region."
5. 
   
6. 
7. From the "Select a country or region" menu, select your new country or region. If you don't see "Select a country or region," contact Apple Support.
8. Review the Terms & Conditions, then click Agree. Click Agree again to confirm.
9. Enter your new payment information and billing address, then click Continue.

It is referring to the setting for the iTunes Store and App Store, not the iTunes app itself. You're supposed to read it as: iTunes-and-App-Store and not: iTunes, and App Store.

Try Media & Purchases, that has the icon for the App Store.

That did the trick for me. Thanks Limnos!