If I buy a power adapter from the online Australian Apple Store, will it match Australian outlets?
Have a look at: Apple World Travel Adapter Kit

If you get the adaptor kit it works with your existing power supply. You just pop off the end you have, and slide on the new end. It's just changing out the prongs for the correct one needed.

Also works with most other Apple products.

This isn't like a normal international adaptor which sits between the socket and the existing plug - it replaces the existing plug.