This should get you nearly there. Concatenate the strings to build your filename and replace it and the file type from a recorded File > SaveAs macro.
Sub ken()
Dim fn As String
fn = ThisWorkbook.FullName
Debug.Print fn, ThisWorkbook.Path
Debug.Print GetBaseName(fn), GetFileExt(fn)
Debug.Print ThisWorkbook.FileFormat
End Sub
Function GetBaseName(filespec As String)
Dim FSO As Object
Set FSO = CreateObject("Scripting.FileSystemObject")
GetBaseName = FSO.GetBaseName(filespec)
End Function
Function GetFileExt(filespec As String)
Dim FSO As Object, s As String
Set FSO = CreateObject("Scripting.FileSystemObject")
s = FSO.GetExtensionName(filespec)
Set FSO = Nothing
GetFileExt = s
End Function
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