Hello Jennie,
Reports are a useful way to organize your transactions in an easy-to-read way to help speed up your work. Going through hundreds of transactions can take time, especially when you need to open each transaction one-by-one. There isn't a report in QuickBooks Desktop that can quite do what you're looking for, but I've got a suggestion that you may be able to work with.
The Transaction List by Vendor report shows you all the transactions related to your vendor, including purchase orders and bills. Using this report, you may be able to cross-reference your purchase order numbers more easily, although there may still be some work involved to double-check your numbers. It may also help to see what other customization options are available to you for narrowing down this report. Check out this article: Customize reports in QuickBooks Desktop
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Let me know if you have further questions. Have a great day!