I ran:
sudo mdadm --zero-superblock --force /dev/sdf1
Then:
sudo mdadm --stop /dev/md0
Next:
[email protected]:~$ sudo mdadm --create /dev/md0 --verbose --level=raid10 --raid-devices=4 /dev/sdf1 /dev/sdg1 /dev/sdh1 missing
So I finally got to this point and this was with help from someone...