I'll have to thread very carefully here, so bear with me. I don't want to make a mistake.

I know there are all these different translations of the names, so I'll try to gather them all here an divide into right ones and wrong ones.

If you've watched both sub and dub anime and read the manga (like me), you might notice how there are all those different names for the army corps. And they might get all mixed up together, you know? There are many. And, sadly, it's not as simple as just one of them is correct. There are many correct ones.

Here's roughly how it goes:

Correct: Survey Corps. Recon Corps. Scouting Regiment. The Scouts.
Wrong: Scouting Corps. Survey Corps Regiment.

Correct: Stationary Corps. Garrison Regiment. The Garrison.
Wrong: Garrison Corps.

Correct: Military Police Regiment. The Military Police. The Gendarmerie.
Wrong: I haven't seen anyone who mixed up this one so far, actually.

Basically, what you want to do if you use more than one of those names, is that you don't want to mix them up to form something new. Simple enough.