NX has a common .prt suffix for all file types; part, drawing and assembly.
There are (at least) two ways to create a drawing in NX - the first way, which is not recommended practice, is to embed the drawing within the part file. This is done by switching to drafting mode and adding the format then the views.
The second, and recommended way, is what they call the 'master model' approach. Using this approach, the drawing is actually created as an assembly, and the components that appear in the drawing are 'assembled' to the drawing. The user then switches to drafting mode and adds views and annotations. The resulting model tree shows the drawing file at the top of the assembly, and the parts are below it as components.
It's a little strange to get used to. The advantage to their approach is that a part can become an assembly at any time just by adding a component to it. This is useful if you've made a model of a plate, created the drawing, and then later decide you need to add a pin to it. You would not need to create a new drawing in this case.
Don't know if this helps your problem, but it may shed some light on how they do drawings.
Ed