The MF 3 (or F3 M) is a true multi-fuel version of the iconic cast iron Jøtul F 3 TD.
You can identify the MF 3 by the following features:
Many parts are shared with the F3 TD.
NB: the F3 TD has a multi fuel conversion kit but it doesn't have its own ash pan.
Open the exploded diagram and visually identify the part you need. Make a note of the position number and quantity needed.
Open the spare parts list and use the position number from the exploded diagram to find a part number and part name.
Translate old part numbers.
The exploded diagrams and spare parts list often have old part numbers, or you might have a cast number on the part in your stove.