Here is the SQL Query:
MERGE  tblProductsSold
USING tblOrders on tblOrders.OrderID = tblProductsSold.txtOrderID
WHEN NOT MATCHED THEN 
Insert ( txtOrderID, txtOrderdate, txtPartno, txtQty)  
values 
(SELECT tblItemsOnOrder.txtOrderID, 
 tblOrders.txtDateTime, 
 tblItemsOnOrder.txtPartNO, 
 tblItemsOnOrder.txtQTY
FROM tblOrders  INNER JOIN tblItemsOnOrder 
ON tblOrders.OrderID = tblItemsOnOrder.txtOrderID
WHERE tblOrders.txtIsConfirmed = '1'
)
OUTPUT $action ;
Desired Result: need to import orders with Products that are not already in the tblProductsSold table