>>76354800 (OP)If you're trying to build muscle then sets of 10–20 reps are good and if you're trying to build strength then sets of 3–5 reps are good. You can do both and not really worry about it. I generally start of heavy and do low reps and then go to a lighter weight and do more reps. Some people consider "powerbuilding" like this an "abomination" but I love it. Do whatever suits your goals.
As for the number of sets, it depends how often you train squats. Try to pic a number of sets where you're doing maybe about 10 sets per week. You might need more or less. Experiment.
And remember, always go to failure or near failure.