The trick with .dwg or .dxf is to open them with a .dft template because the translator only exist in the draft environment. Once you have it open you can either use the "create 3D" tool or copy and paste the lines into a sketch for your part.
When you convert dwg or dxf make sure you have your conversion units set correctly.
File > Open
Then set file type to dwg or dxf as required and click Options button.
Somewhere in there is a setting for conversion units.
I also suggest using the Relationships Assistant to automatically apply relationships to your imported sketch: menu Tools --> Dimension. It's a pain doing it manually. Otherwise SE may give you an error saying your profile is not closed.
BTW not sure of the exact command names because I'm working on a french version.