MIgration from Exchange 2010 to 2013 - Can't delete 2010 databases

Have just migrated all my users to Exchange 2013 and everything has been working well for the last week.  Today I started the process of decommissioning the 2010 box, but I can't delete the databases.  I get the error

The mailbox database 'Mailbox Database' cannot be deleted.

Mailbox Database
Failed
Error:
This mailbox database contains one or more mailboxes, mailbox plans, archive
mailboxes, or arbitration mailboxes......

I ran the command...

get-mailbox -arbitration | Ft Name,"Mailbox Database"

and it returned 5 databases named

FederatedEmail.4c1f4d8b-8179-4148-93...
SystemMailbox{1f05a927-69ce-4c7a-b1c...
SystemMailbox{e0dc1c29-89c3-4034-b67...
SystemMailbox{bb558c35-97f1-4cb9-8ff...
Migration.8f3e7716-2011-43e4-96b1-ab...


I don't know what these mailboxes are and I have no clue of how to move them.  I don't see them in the ECP to migrate.  Really need some help here from the experts.  Need to get this server out of the AD soon.
tparrettAsked:
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suriyaehnopCommented:
Below mailbox created using Exchange 2013 installation. It is a system mailbox

FederatedEmail.4c1f4d8b-8179-4148-93...
SystemMailbox{1f05a927-69ce-4c7a-b1c...
SystemMailbox{e0dc1c29-89c3-4034-b67...
SystemMailbox{bb558c35-97f1-4cb9-8ff...
Migration.8f3e7716-2011-43e4-96b1-ab...

You have to move this mailbox to database hosted on Exchange 2013 DB.

How to move:

https://social.technet.microsoft.com/Forums/exchange/en-US/fb6045fe-22b6-4346-a6c5-09b12744236e/exchange-2013-arbitration-mailbox-moves?forum=exchangesvradmin
tparrettAuthor Commented:
Thanks for the quick responses.  I've split points between both contributors.  I had a much deeper problem than could be described here and eventually had to have Microsoft backdoor the databases.  Could not remove them myself.  Thanks again.
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