If your manufacturer requires both the factory part number and the catalog number on order forms, you will need to do the following:
You MUST have the factory part number in the price list. Ideally, the manufacturer provides you with this information in a way that makes it easy to import. If they send you a price list that you manually cut/paste into OASIS (Copy and Pasting a Price List into OASIS), you will want to ensure you include this column in the process.
Second, you enable the global feature to turn on the print for the PO form. Have an OASIS Admin go to Configuration->Software, then Settings under Global Preferences, Orders Tab, and check the box to "Show manufacturer's part number on orders (when available)."
When you print the order, the factory CSRs can find the information within brackets next to the part number on the order form.