I got help from an expert with a query that provides me the Parent Customer number even if a child account performed the transaction. It works! However, when I add the query into an existing query to provide the columns, it's showing the same invoice number repeatedly, no matter if the customer number is correct or not. The query is called SalesHistory1, and it is attached. the part highlighted in yellow and red is what was added.
Attached is also example of the results