The following code can be inserted on a button click event to copy the product rows to a worksheet called "Orders Placed":
It is important to note that I have only given you enough code to copy these lines, as this was what you weren't sure about. I've left the formatting and other data copying up to you. This code also assumed that the required worksheet already exists, so you may want to perform a check first and if it doesn't exist, then have the VBA code create it for you, and then copy the headings across.
Once your purchase order has been saved, you could then call the following subroutine to reset the purchase order back to its original state:
Hope this helps