Hello breahtone,
Here are few ways on how you can find your saved Purchase Order (PO) in QuickBooks Online (QBO).
First, you can go to the Expenses tab. See the steps on the screenshots.
You can also run a report to list all the POs. Go to the Reports tab then search Purchase Order.
When you are ready you can apply PO to a vendor transactions.
The Community is always here if you need anything else.