Display Barcode, Item Name in Purchase order

Hello Everybody; can someone help me with guidelines on how to show the item barcode and item code on purchase order; what I am looking at is a purchase invoice that shows the barcode and item code for each line item. How do I customize this format and where; I do not find purchase orders among the print format document options.

https://frappe.github.io/frappe/user/guides/reports-and-printing/where-do-i-find-standard-print-formats.html