Please read the forum rules and post your system specs, it can assist us with providing you a good answer.
Do you know why your Uninterruptable Power Supply (UPS) failed? It should have held for at least 15 minutes, unless the battery has failed, been there myself last year. They don't last forever. What kind of UPS is it and how is it connected to your TrueNAS machine?
As for the screen you are experiencing, I'm guessing your boot drive is corrupt. It should be easy enough to fix it by reinstalling TrueNAS on the boot drive and once it boots up, restore your backup configuration file you created from the GUI. That should do it, if not then hopefully you will post the information requested and someone else can offer up some additional help.
Good Luck