Launch FileMaker without opening the file.
Select Recover from the File menu
After the recover is complete, open your older back up copy and use save a copy as... with the clone option to get a copy of your back up that has no records. Open this clone and import all your data from your recovered copy into this back up clone to get an undamaged copy of the file with all your most recent data. You might first run a recover on this older copy to make sure that Recover doesn't identify any issues with it as sometimes there's hidden damage in a file that hasn't affected behavior of your file in any way that you've yet noticed.
- Never use a recovered file if you have any alternative such as an undamaged back up file.
- Make lots of back up copies and retain multiple back up copies going back a long ways in time.