Depends on what you have in your FM files.
DTP Tools has a tool for this: DTP Tools - MIF Filter for Adobe InDesign
… But it doesn't treat mathematical equations !!!!!!
So I've never used it.
I've built my own work process to do this. So, I can convert very complex math FM files (globally, several tens of thousands) to InDesign with FM math equations converted, for me, in totally editable MathMagic équations. And that, without worry!