Keep these backups safe – they are unique to your router’s calibration data (RF tuning, IMEI, etc.).
If you want, I can produce a step-by-step flashing or recovery guide tailored to your MF283U revision and current state—say whether you have model/revision details and access to serial/TFTP.
Before hunting for files, log into your router:
Before attempting any update, you must know what is currently installed.