I think the autorecovery files are deleted when you close FreeCAD normally. It's only when there is a crash, power outage, etc. that the recovery files remain. It makes sense if you think about it, because they're no longer needed presumably if you're able to exit normally. The files, I believe, are kept in appdata/local/temp. To get that folder open file explorer and enter %appdata% in the address bar. This would bring you to appdata/roaming, so you need to then navigate up one level, then go to local/temp. If you see other freecad temp folders, then you know this is probably the right place. Look for a folder called FreeCAD_Doc_37e5f7-abcd-a-bunch-of-hex-digits. In that folder there should be a file called fc_recovery_file.fcstd and another called fc_recovery_file.xml. I don't know for sure if you can just open fc_recovery_file.fcstd or not. Could be the xml file is also needed. (I'm basing this information on what I just found looking in my own temp folder with FreeCAD open and with a document loaded that I've been working on.)
The FCStd1, FCStd2, etc., files are generated as you save your file. If you don't save your file, you don't get those backups. Kinda works like this: when you save your file your old FCStd file becomes your new FCStd1 file. Your old FCStd1 file becomes your new FCStd2 file, and so on. AFAIK, these are not automatically saved. You only get them updated when you save your file.
Why you're getting the errors you're getting, I don't know. It could be you have some logical errors on your hard drive. I would run chkdsk utility. From an administrative command prompt. To get that press Windows+R to open the “Run” box. Type “cmd” into the box and then press Ctrl+Shift+Enter to run the command as an administrator. Then type:
It should tell you it can't do it right now, but it will schedule it on the next startup. If you get that message, go ahead and restart so it can run the test. The /f bit tells it to fix any issues. You can leave that off if you just want to get a report. It can probably run this test without restarting.