You must use an award ticket using your miles - say 125,000 Business or 145,000 miles First, from anywhere in North America to the South Pacific.
See
AAdvantage Participant Airline Award chart. (You can not use AAdvantage miles / copyaments to upgrade on other than American Airlines metal - and AA doesn't go where you want to.) The ward would likely be on AA and partner QANTAS, though awards can be difficult to get on them and they only have Business on the LAX-AKL route, or FJ (Air Pacific, also Business, called Tabua Class,) or TN (Air Tahiti Nui) connecting through either Nadi, Fiji or Papeete, Tahiti, respectively. (In my experience, AKL and BNE seem to be easier to get an award seat than to SYD, or MEL...)