Unit readiness - American Civil War

You say it's been recently reorganized? That is likely to bring the percentage of combat-ready troops up. My initial thought was that it would depend on how many battles they've been in recently. The number of men in units was whittled away by attrition until they were reorganized. In this case, since they've recently been reorganized and in March '64 there hadn't been any significant recent action, I'd think they'd be pretty good on manpower. It's also going to depend on whether there's recently been an illness sweeping the camp, how wet and cold the weather is, and so on. The number of effectives is going to fluctuate wildly based on immediate circumstances. I don't have a good idea on the numbers here, but is an actual number important? Presumably, you want your character to find that the force is either woefully low or surprisingly strong as far manpower. A number isn't necessarily the most effective way to show that.

And are we talking about readiness as far as materiel? The Union would've been quite well supplied. They were in winter quarters still at that point (campaigning didn't begin until, what, April?), so their supply lines were well-established.

The organization of a Union infantry company in the Civil War was (theoretically) as follows:
Captain - commands the company
2 Lieutenants (1st and 2nd Lt - each commands 1/2 of the company - a platoon)
4 sergeants - 2 assigned to each platoon, each commands a section.
8 corporals - 2 under each sergeant, each commands a squad.
80 privates- about 10 to the squad

there were several other members of the company who do not fit into the foregoing organizational pyramid:
1 first sergeant - the highest ranking enlisted man in the company. he handles paperwork, reports, muster rolls, and routine day-to-day administration of the company
2 musicians - one drummer and one fifer - they were frequently minors but since they also frequently lied about their ages, it is hard to say how old they actually were.
one cook - actually a civilian employee of the quartermaster's department - usually black.
one teamster -drives a wagon of company gear/tents - also a civilian

By 1864, the typical company would have had 30-40 present for duty. Besides outright deaths, a number of soldiers would have deserted (about 10% of Union soldiers deserted), plus there would have been any number of medical discharges. A number of soldiers are absent sick in hospital, or on detached duty (for example, a clerk at brigade headquarters or some similar function) etc. Because the company only has a fraction of its authorized strength, the officers and NCO's are likewise not at the authorized level. Frequently, the company is commanded by a lieutenant. Both platoons are led by sergeants. A total of five corporals are available. Only one musician is available - either a fifer or a drummer. The teamster tended to disappear in 1862, when the Union army converted from large wall tents to small "dog tents". The limited amount of baggage still carried (a foot locker with company records, maybe some mess equipment, and some gear for the officers - will not fill a wagon, so 4-5 companies can now share one baggage wagon. The cook is probably still there.

The platoons and squads are not really maneuver elements like in a modern army - your membership in a platoon or a particular squad just determines where you line up. The company maneuvers and fights in formation as a single unit.

If you go to the following link, you will find Bates History of Pennsylvania volunteers - the history of the 75th starts on page 915. It is followed by a roster of the regiment - the roster of company K starts on 943.

https://quod.lib.umich.edu/m/moa/aby3439.0002.001/