The only thing that can replace a C130 is 1.5 C-130's
Australia has ordered 20 C-130J with deliveries starting 2027. How many will we be operating is a grey area. We currently have 12, but these are in the process of being upgraded to latest spec. First upgraded one was delivered last year.
Guessing between the 12 old ones and the new one the RAAF is targetting an operational number of around 24, with the by the time the last 8 new ones arrive they will start replacing the old upgraded one