If any program can reliably convert .fp7 databases to .fmp12 format, it would be FileMaker Pro from which both these file types originate, albeit from different versions. Whenever this conversion is useful or how exactly it is done could not be verified, however no 3rd party database program probably supports FileMaker Pro formats.
Convert FileMaker Pro database to FileMaker Pro database file.
We found 2 software records in the database related to .fp7 to .fmp12 file format conversion.
Microsoft Windows software - convert fp7 to fmp12 on Windows
A program used to create and manage information databases
Convert from fp7 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned fp7 to fmp12. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert fp7 to fmp12 on OS X
A database management program for Mac