Terrain models can be exported to LandXML and 3D Surface in AutoCAD. These formats can also be imported.
The export is carried out by opening a DTM and selecting Export|File - or LandXML. See more about LandXML export.
An import is carried out by opening a new DTM file and selecting Import|File or LandXML. Data from LandXML can be imported in two ways: directly to the document or by importing from the LandXML format.