It appears that eMachineShop software can import DXF CAD files and use them for making its own proprietary designs saved as .ems files. As far as we know, this is the only way how you can produce .ems files, so your only hope.
Convert AutoCAD DXF Drawing Exchange Format to eMachineShop CAD design file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert dxf to ems on Windows
A CAD modeling tool
Convert from dxf file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.