How do I migrate hard drives without losing all my formatting and watch progress?

You cannot do what you want (change the location of the media files) without directly editing the database. [HowTo] Plex database modification - Moving media the right/wrong way - #10 by jelwell

There’s another strategy, but it requires you to keep the number of drives the same.
In short:

  • disable automatic library updates as above
  • stop Plex server
  • copy files from old to new drive, keeping folder names and file names exactly the same
  • remove old drive
  • re-assign the old-drive-letter to the new drive
  • [repeat for the second old drive]