Mastercam has a VB script that allows for batch conversion of .mc8 files from version 8 to .mc8 files from version 9. This seems to be the most convenient way to perform this conversion, especially if you own many older drawings and need to quickly convert them to newer version.
Convert Mastercam V8 file to Mastercam V9 CAD document.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert mc8 to mc9 on Windows
A CAM design software
Convert from mc8 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.