What is the best way to convert .tmp files to .mp3 format?
It's rather unlikely that you will be able to convert random TMP files directly to MP3 Audio Files (.tmp to mp3 conversion), unless they are renamed multimedia files, or a fragments of such files, in which case it might be possible.
Temporary files are generated for many purposes, and even if a TMP file should contain fragments of multimedia data, it is still highly improbable that you will be able to convert TMP to MP3.
You can always try renaming your file's suffix from TMP to MP3, and try to play it using a common media player, but your chances are quite low.
The database currently does not contain any tmp software converter.