Check out some options how kml files might be converted to scn format.
Home > Search converters: kml to scn
Search for kml to scn converter or software able to handle these file types.
Unfortunately, we do not know about any possible kml to scn conversion, beyond the fact that you can indeed import KML/KMZ files to AutoCAD which uses .scn files. But it seems these files are just definitions and not something you can use for CAD/3D model conversions.
But numerous .scn files exists, so perhaps some other, different reason why to convert kml to scn exists.
Unfortunately, there is no detailed software record in the database that match this conversion.
Additional links: kml file extension details, scn file extension details
KML
Files with kml extension can be usually found as navigation/map files saved in Google's KML (Keyhole Markup Language) file format.
SCN
An scn file extension is related to CAD programs developed by Autodesk. An scn file stores surface slope definition.
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