Regarding for luggage, can please tell me in au$?

If your checked luggage exceeds 23kg but less than 32kg, yu should pay extra CNY1000 (around 198 Australian dollars) per piece. If it is between 32 to 45kg, you need to pay CNY3000 (AUD 596) per piece.

If your checked luggage doesn't exceed the weight limit (23kg) but exceed the total quantity, CNY 1000 (AUD 198) is charged for the first piece in addition to the standard allowance, CNY 2000 (AUD 397) for the second piece or more in addition to the standard allowance.

All the above information is found from the website of China Southern Airlines. I can't guarantee that it's the latest. Perhaps, you can contact the airline to confirm this.