Most GP users are familiar with the SOP-to-POP integration with which you can easily create a PO from a Sales Order. However I'm guessing that most users don't know that a similar function exists with which you can easily create PO's for a large number of sales documents at one time.
This is how you do it:
Navigate to the Sales Inquiry Restrictions screen: Inquiry >> Sales >> Restrict Sales Documents.
Create a range to select all the sales documents you want to be considered when creating PO's. You can create a new one or use an existing inquiry.
Click on the "Inquiry" button.
This screen will pop up that shows all the sales documents selected.