Welcome and thanks for visiting the Community, @info-securedlivi.
The Purchase Order (PO) option is only available in both QuickBooks Online (QBO) Plus and Advanced versions. If you're using Simple Start, here's how to upgrade your account:
After that, you need to turn on the PO feature in your new account. Here's how:
If you want to more about using PO in QBO, I highly suggest checking out this article: Create purchase orders. It also includes the types of reports that you can pull up.
You also have the option to add PO to cheques or Bills. Refer to this article for further guidance: Apply a purchase order to a supplier transaction.
Please let me know if you have any other questions or concerns. I'll be more than happy to help. Have a great day!