How to copy data from two workbooks and append to another workbook?

I ran this code from a separate macro (.xlsm) enabled workbook

Try this code

Sub CombineWBks()
  Dim strFirstFile, strSecondFile, strThirdFile As String
  Dim wbk1, wbk2, wbk3 As Workbook
  
'Speeding up the macro
    Application.ScreenUpdating = False
    EventState = Application.EnableEvents
    Application.EnableEvents = False
    CalcState = Application.Calculation
    Application.Calculation = xlCalculationManual
    PageBreakState = ActiveSheet.DisplayPageBreaks
    ActiveSheet.DisplayPageBreaks = False
    Application.DisplayAlerts = False
    
'Change file path to match your files locations
    strFirstFile = "C:\_ExcelForum\CombineWorkbooks\Workbook 1.xlsx"  'Change to your location & ensure the workbook exist
    strSecondFile = "C:\_ExcelForum\CombineWorkbooks\Workbook 2.xlsx" 'Change to your location & ensure the workbook exist
    strThirdFile = "C:\_ExcelForum\CombineWorkbooks\Workbook 3.xlsx" 'Change to your location & ensure the workbook exist
      
      Set wbk1 = Workbooks.Open(strFirstFile)
      Set wbk3 = Workbooks.Open(strThirdFile)

'Clears data within sheet1 of the third file
         'wbk3.Sheets("sheet1").UsedRange.ClearContents 'Clears the third file's data (used only for testing}
         
'Copy process begins
          wbk1.Sheets("Sheet1").Range("$A:$E").Copy wbk3.Sheets("Sheet1").Range("$A:$E") 'Change the Sheet name and data range accordingly
          wbk1.Close
  
      Set wbk2 = Workbooks.Open(strSecondFile)

          wbk2.Sheets("Sheet1").Range("A2:E500000").Copy wbk3.Sheets("Sheet1").Range("A" & Rows.Count).End(xlUp).Offset(1, 0) 'Change the Sheet name and data range accordingly
      
          wbk3.Save
          wbk3.Close
          
'Restoring Speeding up the macro
    Application.ScreenUpdating = True
    Application.EnableEvents = True
    Application.Calculation = xlCalculationAuto
    ActiveSheet.DisplayPageBreaks = True

End Sub