It looks like both .flb and .fmp3 files are used by FileMaker Pro and thus if any program could somehow (if even) convert them, it would be this program. However, we haven't found any specific information about this conversion, if it actually works somehow.
Convert FileMaker Pro label file to FileMaker Pro for Mac document file.
We have found 2 software records in our database eligible for .flb to .fmp3 file format conversion.
Microsoft Windows software - convert flb to fmp3 on Windows
FileMaker Pro for Windows is easy-to-use database software used to create and manage information databases.
Convert from flb file
to fmp3 file
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 flb to fmp3. 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 flb to fmp3 on OS X
File Maker Pro for Mac is easy-to-use database tool used in business, government, and education to manage their information in databases.