Restore Mailbox on Exchange 2010 SP1

Hi,
I have Exchange 2010 SP1 on Windows 2008 R2 Ent. Server.
i have two Mailbox DataBases and two Mailbox Archive DataBases.
some of useres we diable an online archiving for them , then when we enabling it again we found that an emply new online archive folder, while the old online archive data for them already existing on Archiving Mailbox DataBase.

we try to use "New-MailboxRestoreRequest" cmdlet as following:

New-MailboxRestoreRequest -SourceDatabase "Archiving Database 1" -SourceStoreMailbox "Online Ar
chive - Mostafa Naghy" -TargetMailbox MTest.User@mydomain.com -AllowLegacyDNMismatch

but the result is the following error:

Mailbox "Online Archive - Mostafa Naghy" isn't unique on database "Archiving Database 1".
    + CategoryInfo          : NotSpecified: (0:Int32) [New-MailboxRestoreRequest], ManagementObjectAmbiguousException
    + FullyQualifiedErrorId : B24C21A,Microsoft.Exchange.Management.RecipientTasks.NewMailboxRestoreRequest

we run the following cmdlet         Get-MailboxStatistics -Database "Archiving Database 1"

the result is :

DisplayName               ItemCount    StorageLimitStatus
-----------               ---------    ------------------
Online Archive - Mosta... 13560                NoChecking
Online Archive - Mosta... 0                    BelowLimit
Online Archive - Ahmed... 77                   BelowLimit
Online Archive - Ahmed... 0                    BelowLimit

as above there are two online archiving for each mailbox.

Please anyone help me to remove the mailboxes with [ItemCount=0] and make the online archive mailboxes unique on database to complete the "New-MailboxRestoreRequest" cmdlet?

Thanks.