In order to delete those orgs, you will need to make sure:
- That all licenses are expired. If you have active licenses and you need to delete the org, you could move those licenses in another org. Just note that if you are using the Co-termination licensing model it will change the expiration date of that org.
- That all devices are removed from the networks. You can still remove devices from disabled networks.
- That all networks are deleted.
- That only one full org admin is left in that org.
Once you have verified the above, you can delete the org from Organization > Settings. At the bottom of the page there is a "Delete organization" button.
BR,
Ioana