I would suggest that you use a free tool called MPEG Streamclip, available here. Get the Beta version.
Drag your .mod clip into MPEG Streamclip. The, use FILE/EXPORT USING QUICKTIME. Choose Apple Intermediate Codec as your video codec. Save it where you can find it.
In iMovie, import using FILE/IMPORT MOVIE.
If you have a large number of mod clips, MPEG Streamclip has a batch mode.