Seems all format files from GemCad are not reloaded by any progs! :(
too old versions!
Not evident prog! :)

Edit
I have found a workaround!
Import the DXF inside the free Pcon Planner! https://pcon-planner.com

Export as OBJ & double faces! (curiously exported as DXF is not reloaded by Moi ! )
_import OBJ... (by Max Smirnov)