Give this a try:
Private Sub PO_Click()
Dim exists As Boolean
Dim tabtitle As String
tabtitle = ActiveCell.Value & ActiveCell.Offset(0, -1)
For i = 1 To Worksheets.Count
If Worksheets(i).Name = tabtitle Then
Worksheets(i).Activate
exists = True
End If
Next i
If Not exists Then
Sheets("PO Template").Range("B5").Value = ActiveCell.Value
Sheets("PO Template").Copy Before:=Sheets(8)
Sheets("PO Template (2)").Name = tabtitle
Sheets(tabtitle).Range("B6").Value = Application.WorksheetFunction.XLookup(Sheets(tabtitle).Range("B5").Value, Sheet8.Range("A2:A2000"), Sheet8.Range("B2:B2000"))
Sheets(tabtitle).Range("B7").Value = Application.WorksheetFunction.XLookup(Sheets(tabtitle).Range("B5").Value, Sheet8.Range("A2:A2000"), Sheet8.Range("c2:c2000"))
Sheets(tabtitle).Range("E7").Value = Application.WorksheetFunction.XLookup(Sheets(tabtitle).Range("B5").Value, Sheet8.Range("A2:A2000"), Sheet8.Range("d2:d2000"))
Sheets(tabtitle).Range("G7").Value = Application.WorksheetFunction.XLookup(Sheets(tabtitle).Range("B5").Value, Sheet8.Range("A2:A2000"), Sheet8.Range("E2:E2000"))
Sheets(tabtitle).Range("B8").Value = Application.WorksheetFunction.XLookup(Sheets(tabtitle).Range("B5").Value, Sheet8.Range("A2:A2000"), Sheet8.Range("f2:f2000"))
Sheets(tabtitle).Range("B9").Value = Application.WorksheetFunction.XLookup(Sheets(tabtitle).Range("B5").Value, Sheet8.Range("A2:A2000"), Sheet8.Range("g2:g2000"))
End If
End Sub