Well, it's not as hard as you think.
To those who will not get a word of what I'll say, I included screenshots showing the steps for the same Slap Bass sound (from Sonic 1, Green Hill Zone) :
When you dumped your channels using Gens KMod, you should have some *.y12 files somewhere on you hard drive (where you specified the files to be saved):
Go to that menu using Gens KMod.
To dump your voice/preset/sound, just hit the "Dump channel" button.
Then, open MVSTracker MD. Go to the "View" menu and select "Instrument Editor".
Push the "Load" button at the top of the dialog and select the y12 file you want.
Now, all parameters necessary to set up you voice should be loaded:
VOPM uses the exact same scale for FM values. The only probem is that op2 and op3 are inverted (order must be actually op1, op3, op2, op4 to make the sound sound right in VST synths such as FM7 or VOPM).
To port the voice to VOPM, open your music tool (Fruity Loops or whatever) and select VOPM as a new instrument (in Fruity Loops/FL studio, "New Channel" --> "VOPM").
Once, you have the VOPM window, select en empty preset where you can create a new sound.
Now, simply set up your voice/sound/preset by copying the values displayed in the instrument Editor of MVSTracker MD.
Operator order is the following (VOPM / MVSTracker MD):
M1 = Slot 1
C1 = Slot 3
M2 = Slot 2
C2 = Slot 4
Other parameters have different names but I think it should be easy to identify what is what.
Once you've finished, hit the "Export" button on the top left of the VOPM window and save your bank to hard disk. (you can save single presets in fxb format in FL Studio, too):
I hope this should help you.