When trying to convert .DWG files to .DXF, there are several resources to use. This article will cover how to convert between the two sing AutoCAD Civil3D software, as well as an online resource. With the accessibility to AutoCAD, open the .DWG file you are looking to convert. Once opened, in the the file menu, select "Export", DXF option, and choose the year of CAD that you would like to reference.
Once chosen, the file will download to your computer to as a .DXF file.
Another resource to do this is: