Welcome to the Community!
I want to ensure I've got the right information about your concern to provide the most accurate resolution. Are you referring to using custom purchase order numbers in QuickBooks Online? Also, could you please provide more details about what you want to be displayed when creating a purchase order? Any additional information and relevant screenshots about your concern would help me provide the best assistance.
Your cooperation is greatly appreciated. I look forward to hearing back from you soon so we can resolve this matter as quickly as possible.