Do you want to move all the mailboxes from one mailbox database to another? You can do this easily by using the following command:

 Get-MailboxDatabase  <Source Mailbox Database> | Get-Mailbox | Move-Mailbox -TargetDatabase  <Destination Mailbox Database>

You can even use wildcard characters with the Get-MailboxDatabase cmdlet to consolidate mailboxes from multiple source mailbox databases into a single destination mailbox database.

Powershell make no sense to me…