EPIC multi-bitmap image format (*.mbm) is rather uncommon and not widely supported in graphics programs. Yet some dedicated image converters like the XnConvert support it and can export to other bitmap formats including the JPG. So this is probably your best bet for the MBM to JPG conversion.
Convert EPOC multi-bitmap picture to JPEG bitmap image format.
We found one software available in the database for this conversion.
Multiplatform software - convert mbm to jpg on any platform
Cross-platform batch image transcoder compatible with 500 picture image formats
Convert from mbm 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.