This conversion is more of standard backup procedure done using Family Tree Maker in which a .fbk backup is generated from a .ftw file. You cannot do this in other programs, and there most likely also is no reason why you would want to do that in any 3rd party program.
Convert Family Tree Maker project to Family Tree Maker backup file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert ftw to fbk on Windows
A popular genealogy software with almost 20 years of development
Convert from ftw 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.