To change the automatic database backup filename, go to the VPOP3 settings, then Settings → Database → Backups.
The Dump Command Target File option tells VPOP3 where to store the backups, and what to call them. The default is DBBack-%w.dmp. You could change this to “DatabaseBackup.dmp” or whatever you prefer.
In the default filename, then %w is replaced by the weekday-number (0=Sunday, 1=Monday, etc)