Upgrading to new watch
Do I unpair my existing watch before pairing my new watch?
Question marked as
Yes. As that will create a backup of your current watch, so you can then set up your new watch from the backup of your previous watch.
If you are planning to sell, trade or give away your watch, see these instructions --> What to do before you sell, give away, or trade in your Apple Watch, or buy one from someone else - Apple Support