Method Invocation failed because [Deserialized.Microsoft.Exchange.Data.ByteQuantifiedSize] does not contain a method named ‘ToMB’

Scenario: When connecting to Exchange PowerShell without the Exchange management tools installed, you get the following error message when trying to convert the mailbox size to another Size unit.   For example:  With the Exchange Management tools installed,  you can run the following command successfully:

Get-MailboxStatistics  user1 | Select {$_.TotalItemSize.Value.ToMB()}

But when you connect to Exchange Powershell via a session without the Exchange Management tools installed, you receive the following error:

Method Invocation failed because [Deserialized.Microsoft.Exchange.Data.ByteQuantifiedSize] does not contain a method named ‘ToMB’

Solution:  To work around this problem:

#Collect Mailbox Stats
$stat_o365 = get-mailbox -resultsize unlimited | Get-mailboxstatistics

#Loop the stats
$stat_o365 | %{
$Name = $_.displayname
$TIS = [string]$_.TotalItemSize
$TDIS = [string]$_.TotalDeletedItemSize

#start the value manipulation
$regex = [regex]"((.*))"
$TISstring = [regex]::match($TIS, $regex).Groups[1]
$TDISstring = [regex]::match($TDIS, $regex).Groups[1]
$TISString = $TISString -replace "Bytes",""
$TDISString = $TDISString -replace "Bytes",""

#Convert the strings to Int
$TDISValue = [INT]$TDISString
$TISValue =  [INT]$TISString

#Add the Mailbox Size and round to the nearest MB
$TotalSize = [Decimal]::Round((($TDISValue + $TISValue)/1024)/1024)
}