If you wipe drive C:, then you wipe your Plex data with it.
You could move this data to a different drive: [HowTo] An extended guide on how to move the Plex data folder on Windows
But even then you should at least make a backup of the Plex server branch of the windows registry, before wiping drive C: again: Backing Up Plex Media Server Data | Plex Support
After getting your Windows up and running again, you double-click this .reg file.
Then you install Plex server.
