Can’t pair my watch 3 with iPhone 12 pro

I have a watch 3 that I am wanting to pair with my new 12 pro. New phone will not pair. My old X has been given to my son and his old 8 transferred in to the x and does not show my watch on it any longer. Is the 3 not comparable with the 12 pro?? I would reset, but won’t I lose all of my data from the watch?