Srilankan passport holder in australia, how many visa do i need?

Deshi, according to Chinese embassy in Australia, they accept applications for Macau and HK. However, you should submit your application to the Chinese consulate that has jurisdiction over the place you currently stay at. Of course you should apply two, one for HK and the other for Macau. If Chinese consulate doesn't accept your application for HK, then you have no choice but post your application to HK Immigration Department. It will take four to six weeks.

I personally think you should submit your applications at least 1.5 months ahead of your trip. It's possible that Chinese consulate might transfer your application to HK.