I've got a similar set up, currently running Plex on a Windows 10 PC, so have been looking at this too. My understanding is that we'll need to format the drives so that will wipe the data, not seeing any way around that.
Saw someone had a similiar question about moving from unraid to hex and an admin confirmed no way to do it without deleting the data, so I assume that would be the same going from a Windows -