Hello. My name is Michael. I can assist you with your question. In this situation, there is only really one thing you can try to do, which is to repair the backup or disk - depending on where the problem is.
You can use Disk Utility to verify your startup disk, your backup drive, and any other drives you're trying to back up. Turn off Time Machine, then connect any drives you're using as part of your backup.
You can turn Time Machine back on after your drive is verified as ok, or repaired successfully.
If Disk Utility finds issues it can't repair, see Using Disk Utility to verify or repair disks for more information on the next steps to try. It's possible the drive might need to be reformatted, or the backup is damaged.
DO NOT do a format at this point as that will erase the drive. If it comes to that point, there may be other options (although expensive) that can be used to recover the data.