Just delete them, preferably with FF closed otherwise some may be locked. They seem to be sqlite3 temporary files and really Mozilla should clean them up when closed.
Ideally is a script to clean %TMP% when booting up or what I did is have %TMP% on a ramfs.ifs volume.
Okay, that explains why I didn't find any. I use the PAE Ramdisk from the QSINIT package for %TEMP%, and it, of course, gets wiped clean at every boot.
The %TEMP%, %TMP% and %TEMPDIR% entries in CONFIG.SYS usually point to the same place, and that location should contain only currently open temporary files. Programs are supposed to clean up after themselves, but there are a number of reasons why they don't. As noted, a user should take steps to clean that out, on a regular schedule (at each boot is good).
I have heard of people who use the %TEMP% directory as temporary file storage, and that is a very BAD idea.
There are a couple of other places where files collect. SAMBA leaves log files in C:\MPTN\ETC\samba\log\Archive and C:\MPTN\ETC\SmbBackup, forever. You may want to keep a few of the latest ones, in case you need them, but hundreds of them are a bit much.