howto assign variable from ps

gistfile1.txt

# want to switch from old method using  Get-MailboxStatistics cmdlet to using Export-MailboxDiagnosticLogs instaed
# as shown at ( https://petri.com/exchange-online-exposes-new-mailbox-activity-data ) 

#old method using  Get-MailboxStatistics cmdlet
    $UserReport = New-Object PSObject    
    # check for mailbox info
    foreach ($mbx in $mbxs) {
      if ($user.UserPrincipalName -eq $mbx.UserPrincipalName) {
        $mbxstats = Get-MailboxStatistics -Identity $mbx.UserPrincipalName -ErrorAction SilentlyContinue | Select LastUserActionTime,LastLogonTime,SystemMessageSize
        $LastUserActionTime = $mbxstats.LastUserActionTime
        $LastLogonTime = $mbxstats.LastLogonTime
        $SystemMessageSize = $mbxstats.SystemMessageSize
        
        #Last User Action Time
        If($LastUserActionTime -eq $null){ 
          add-member -inputobject $UserReport -membertype noteproperty -name "User Action Date" -value "No User Action"
          add-member -inputobject $UserReport -membertype noteproperty -name "User Action Time" -value "00:00"
         }
        Else{ 
          add-member -inputobject $UserReport -membertype noteproperty -name "User Action Date" -value $LastUserActionTime.ToShortDateString()
          add-member -inputobject $UserReport -membertype noteproperty -name "User Action Time" -value $LastUserActionTime.ToShortTimeString()
         }

        #Last Logon Time
        If($LastLogonTime -eq $null){ 
          add-member -inputobject $UserReport -membertype noteproperty -name "User Logon Date" -value "Never Logged In"
          add-member -inputobject $UserReport -membertype noteproperty -name "Last Logon Time" -value "00:00"
         }
        Else{ 
          add-member -inputobject $UserReport -membertype noteproperty -name "Last Logon Date" -value $LastLogonTime.ToShortDateString()
          add-member -inputobject $UserReport -membertype noteproperty -name "Last Logon Time" -value $LastLogonTime.ToShortTimeString()
         }

        # SystemMessageSize
        If($SystemMessageSize -eq $null){ 
          add-member -inputobject $UserReport -membertype noteproperty -name "Message size" -value "No size"
         }
        Else{ 
          add-member -inputobject $UserReport -membertype noteproperty -name "Message size" -value $SystemMessageSize.Value
         }
        
     

# new method using Export-MailboxDiagnosticLogs instead 

        $mbxstats = Export-MailboxDiagnosticLogs -Identity $mbx.UserPrincipalName -ExtendedProperties -ErrorAction SilentlyContinue 
        $mbxstats = [xml]($mbxstats.MailboxLog)
        
        # how do I now set the  $LastUserActionTime $LastLogonTime  $SystemMessageSize
        # the following does not work - (obviously)
        
        $LastUserActionTime = $mbxstats.LastUserActionTime
        $LastLogonTime = $mbxstats.LastLogonTime
        $SystemMessageSize = $mbxstats.SystemMessageSize

        # the new data type is System.Xml.XmlElement
        LastUserActionTime |  Get-Member:  

        Name  : LastUserActionTime
        Value : 11/06/2020 09:19:25

        LastUserActionTime:  System.Xml.XmlElement
        
        # I can display all Last.... times using the code in the webpage 
        $mbxstats.Properties.MailboxTable.Property | ? {$_.Name -like "Last*"}
        
        # But how do I now assign the 3 variables ( $LastUserActionTime $LastLogonTime  $SystemMessageSize ) as in the old method at the top? Will want to split time it into two parts a Date and a Time part again and the Size into a value
        add-member -inputobject $UserReport -membertype noteproperty -name "User Action Date" -value $LastUserActionTime.ToShortDateString()
        add-member -inputobject $UserReport -membertype noteproperty -name "User Action Time" -value $LastUserActionTime.ToShortTimeString()
        add-member -inputobject $UserReport -membertype noteproperty -name "Message size" -value $SystemMessageSize.Value

        # what is the correct 'new' syntax to use for setting to the same type of values and tyes?
        $LastUserActionTime = 
        $LastLogonTime = 
        $SystemMessageSize =