Create Table #Temp1( DisplayName Nvarchar(256), ItemCount Bigint,TotalItemSize Bigint)
Insert into #Temp1(DisplayName,ItemCount,TotalItemSize)
SELECT DisplayName,ItemCount,TotalItemSize
FROM OpenExchangePSQuery(
    POWERSHELL, '
    Get-Mailbox | Get-MailboxStatistics | Sort-Object totalitemsize -desc | Select DisplayName,ItemCount, TotalItemSize
 
              ', POWERSHELL
)


Select DisplayName,ItemCount,dbo.MB(TotalItemSize/1024) as 'total item size (GB)'
From #Temp1