VP6 is now a discontinued format, replaced by VP8, yet it is still supported in some video converters and can be transcoded to other video formats, including MPEG-4. Some good choices are listed below, but the as was said, the support for this format is rather limited.
Convert VP6 encoded video file to MPEG-4 video file format.
We found one software available in the database for this conversion.
Apple macOS / Mac OS X software - convert vp6 to mp4 on OS X
Universal video converting software for Mac
Convert from vp6 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.