If you are using standard AutoCAD (not Civil 3D) and cannot find the KML export button, you can still utilize the spatial engine:
Output Tab=>Map Data Transfer panel=>DWG to SDF icon=>change files of type to Shape Multiclass=>browse to and select the folder. [ Autodesk Community, Autodesk Forums, Autodesk Forum Export DWG from AutoCAD to Shapefile (SHP) export spatial data autocad
Requires third-party plugins like Spatial Manager to handle geospatial formats. If you are using standard AutoCAD (not Civil