Exchange 2013: This mailbox database is associated with one or more active mailboximport / Cannot uninstall exchange

We have a corrupted installation of Exchange 2013 due to installating CU6

New Exchange server is already installed and mailboxes are migrated over, I am now in the process to uninstall the old exchange 2013 so we can decomission it but I get this error when I try to run uninstall

"This mailbox database is associated with one or more active mailbox import,To get a list of all Mailboximport request associated with this database, run Get MailboxImportRequest | ?{ $_.RequestQueue -eq "<Database ID>"}....

But when i run this command I get an error of" The Get-MailboxImportRequest is not recognized as a cmdlet...

Any advise is appreciated

Thanks.