How to get out of the Windows Insider Program

I keep getting a message that my insider copy of windows 10 is about to expire. I no longer want to be on insider builds, so I followed Microsoft's help page to "Reset" the PC but it said the files were not trusted and that a certificate may have expired. There was no information on how to fix this.

So I guess I have to completely reinstall windows 10 (I don't want 11 yet).

Is there a step by step walkthrough on how to backup personal data and re-install windows in Parallels? I'm also confused about the relationship between windows reinstalling and the data stored in the Mac portion of my hard drive (outside of the VM). I'm assuming this isn't touched, but just want to make sure.