I haven't imported 3d Cadence files into 2001 but have been making good progress over the last week or so using and understanding Pro/ECAD to import EMN and EMP (IDF format) files exported from PowerPCB.
In Cadence, export IDF from Cadence, change the format to PTC. I usually click on the filters button and filter out vias etc. This gives you 2 files, and ENM file which is the board and placement data and a EMP file which is the library file.
I have found the best way is to make sure that the ProE model names match the Cadence symbol names. This isn't essential but it saves time.
You also need to make sure that the coordinate system on your models match the position and orientation of the Cadence symbol, eg X, Y & Z point in the same direction.
Once this is correct you are ready to import.
Open the ENM file and choose to create an assembly. The PCB profile will be generated. If there is any overlapping or gaps in the geometry ProE will ask you if you want to modify using sketcher.
Once the profile is ok, ProE will automatically ask you for a EMP file. Find the correct file and ok.
If you model names & orientation match the PCB symbols then everything should be fine. If not, then open the ECAD_HINT.ADD file. Now change the MCAD NAME to your model names. Rename the ECAD_HINT.ADD file to ECAD_HINT.MAP.
Now go INSERT, DATA FROM FILE choose the EMN file first then ProE will prompt you for the EMP file. Hopefully that should be it!