Why when I import model as skeletal mesh it loads as parts?

Sorry for my bad English.
I am from Russia and I don’t know English well.

It could be that you haven’t combined your mesh before exporting. I use this for example to make a house with a door that ends up as two models so I can add a physics constraint to the door while not having to rescale it to make it fit. Simply by not combining the door mesh and the house mesh before importing.