IAM

IAM (Autodesk Inventor assembly) is one of the native file formats of Autodesk Inventor, along with IDW (Autodesk Inventor drawing), IPN (Autodesk Inventor presentation), and IPT (Autodesk Inventor part). Assemblies consist of arrangements of parts.

Apparently the Autodesk Inventor software has new versions yearly with incompatible file formats, where they're nice enough to provide updates to the version one year earlier to patch them to load the next year's files, but any further out of date and you're out of luck dealing with their planned obsolescence.

Links

 * Autodesk Inventor (IPT, IAM) Files (Autodesk knowledge base)
 * How to export Inventor assembly files and open them in Fusion 360
 * To Work with Assembly Files One Year Newer