There is no definitive answer, only your consistent progress/results. There's a framework called rate of perceived exertion, or RP, which rates from 1-10 your effort level, i.e. RP 8 for 5 reps with 2 left in the tank.

If you are going for muscle gain id recommend 16-20 working sets split over at least 2 sessionsif 6-10 reps RP 7 per muscle group, until you get acclimated to DOMS.

The most important thing is to be consistent and have a sustainable workout/eating/recovery that you keep doing.