size comes with strength and food.
squat heavy with good form.
reps of 6 are good.
so are reps of 10 or 5 or 3 or the odd occasion 20.
Point is, unless you are warming up, you should be lifting heavy.
If you're new to lifting the usual 3 sets of 10 is good.
heavy weights create strength. that is why the likes of 5x5 programs are so common and so frequently recommended.
as you get stronger, you will also get bigger.
endurance?? see marathon runners.. no squats there.