Need to save the .xls file as .xlsx without opening it through VBA code in outlook

Sub SaveLatestAttachment()
Dim olApp As Outlook.Application
Dim oMail As Outlook.MailItem
Dim NS As Outlook.NameSpace
Dim oFolder As Outlook.Folder
Dim SaveInFolderName As String
Dim SaveInFolder As String
Dim subFolderName As String
Dim strFile As String
Dim Item As Object
Dim Items As Outlook.Items
Dim x()
Dim i As Long
Dim xlApp As Object
Dim wb As Object
Dim strFileNew As String

SaveInFolderName = CreateObject("WScript.Shell").SpecialFolders(16)
subFolderName = "EmailAttachments"
SaveInFolder = SaveInFolderName & "\" & subFolderName & "\"

Set olApp = New Outlook.Application
Set NS = olApp.GetNamespace("MAPI")
Set oFolder = NS.GetDefaultFolder(olFolderInbox).Parent.Folders("Test")
ReDim x(1 To oFolder.Items.Count, 1 To 4)
Set Items = oFolder.Items
Items.Sort "[ReceivedTime]", True
For Each Item In Items
    If TypeOf Item Is Outlook.MailItem Then
        Set oMail = Item
        If LCase(oMail.Subject) = "my daily report" Then
            If oMail.Attachments.Count > 0 Then
                For i = 1 To oMail.Attachments.Count
                    strFile = oMail.Attachments(i).FileName
                    If InStr(LCase(strFile), "my report") > 0 Then
                        strFile = SaveInFolder & strFile
                        On Error Resume Next
                        Kill strFile
                        On Error GoTo 0
                        oMail.Attachments(i).SaveAsFile strFile
                        strFileNew = Replace(strFile, ".xls", ".xlsx")
                        Set xlApp = CreateObject("Excel.Application")
                        Set wb = xlApp.workbooks.Open(strFile)
                        xlApp.Application.DisplayAlerts = False
                        wb.SaveAs strFileNew, 51
                        wb.Close True
                        xlApp.Quit
                        Set xlApp = Nothing
                        Kill strFile
                        GoTo ExitSub
                    End If
                Next i
            End If
        End If
    End If
Next Item
ExitSub:
Set olApp = Nothing
MsgBox "Task Completed Successfully.", vbInformation
End Sub

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