Sage 50 Canada

I am importing data into Sage from a 3rd party software. Each of the transactions has a BOL# associated to it. When the data is imported, the quantity, product, price, etc. all import correctly - but I am unable to find a field in Sage 50 for a transaction…

Is there a spot to enter a customers Purchase Order number on a Sales Invoice? Seems to me its a very important piece of an order, yet I can't find where to enter it for my customers ! (I have Sage 50 Premium)