Freehand is an illustrator program, and it's quite unlikely you can 'convert' artwork to native InDesign stuff.
However, it should not be necessary. I don't think you can import (“Place”, in Indesign's parlance) native Freehand documents in InDesign (– have you tried?), but it should be possible to save the original files as something you can place in ID: Adobe Illustrator AI, PDF, or (when all else fails) EPS.
Adobe on Freehand: “No updates to FreeHand have been made for over four years, and Adobe has no plans to initiate development to add new features or to support Intel-based Macs and Windows Vista.”
If you want to be able to edit the files in a more modern package, try converting it to Illustrator instead. That should not be a problem at all, since Illustrator is an artwork design package as well. You can try opening the original file immediately, or use one of the other file types as above.