As IMF music is 100% synthesised, converting the notes into their MIDI equivalents is relatively easy, but choosing the correct MIDI instruments is not. Most of the time this requires a good deal of trial and error, and the final MIDIs will always sound different than the IMFs for this reason. This is not to say the conversion doesn't work, it just sounds quite different.
imf2midi file.imf file.mid
There are a few different pages archiving IMF2MIDI - one of them is: