Try something based on:
Sub Demo()
Application.ScreenUpdating = False
Dim Tbl As Table, Cll As Cell
For Each Tbl In ActiveDocument.Tables
  For Each Cll In Tbl.Range.Cells
    If Cll.Tables.Count > 0 Then
      With Cll.Tables(1)
        MsgBox .Rows.Count & vbTab & .Columns.Count
      End With
    End If
  Next
Next
Application.ScreenUpdating = True
End Sub