Hello disk1 is mounted as normal (stand alone disk since you started by formatting the disk). You do not need to format a disk to aad it to /configure raid. Please read the manuals on how to replace a raid disk.
In this case remove disk and re-insert next select disk and configure (to add to raid).
In any case, What is the raid array ? if it is raid 5 , you have to start an new configuration since your current configuration can not be recovered with (2 or more) disks failed or disconnected