STP file format..

This format works with the software:

IMSI TurboCAD Deluxe 21
ideaMK STP Viewer
Autodesk Fusion 360
Dassault Systemes CATIA
LKSoft IDA-STEP
STEP Tools STEP File Browser
FreeCAD
CADSoftTools ABViewer

If you have broken file, ask admins of this site, they can help you. They are online from 8:00 to 16:00.

Thank you!!!
I found some conversion software that works rather well!
ABviewer 11