There are ostensibly 42 figures in a box;
2 command sprues, each with a musician and two officers.
There are 3 sprues of infantry. Each contains 8 musketeers and 5 pikemen. However, there are only 4 pikes per sprue. So each box actually contains 24 muskets, 12 pikes, 6 command and 3 spare figures.
What almost everyone does is use the extra arms to convert the spare figures into extra command or musketeers.
Of the pike figures, one is armoured/thrusting and so defn a pike. Two are marching carrying the pike -- you can convert them to muskets using the loose muskets from the cavalry boxes. Two are "thrusting" poses and actually can work quite well as musketeers (if you ignore they have no bandolier).
I ended up getting two boxes of infantry and two battalia packs. That's made 8 units of infantry -- needing to make extra command. You can put fifer arms on a marching musketeer to get an extra musician. You can get extra sword arms from the cavalry sets to make infantry leaders[1]. It's obviously easy to give a marching pikeman a standard instead.
More seriously, there are only 2 morions per sprue, so you'll need to get metal ones to equip all the pike. Again if you get enough boxes and want to make scots, you can just swap bonnets for helmets..
[1] They look quite good with a sword arm on the right and a marching musket arm on the left -- I've started adding these leader figures to my shot sleeves just for character.