How many sets are you suppose to do while working out?

I got my reps down pack and I've done a lot of research for this whole thing. I'm trying to get bigger thighs and glutes. I alreasy got me a workout plan and the reps down pack (including weights) its just the sets. I've heard that one set is literally goung to get you the same results as if you did three sets. Then i heard three sets is perfect. Then people keep saying two sets. How many sets do i nees?
How many sets are you suppose to do while working out?
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