If you go to print a bill of lading after loading a shipment through the warehouse module and you get an error message “Item xxx must have an NMFC number.” then you can follow these steps to locate where you set it up in AX.
The NMFC code is a designation of commodities that allows transport companies to compare and evaluate goods for shipment. You can read more about it on their website. http://www.nmfta.org/pages/nmfc. These codes are often used in LTL (Less than truck load) shipping typically in North American.
There are tools like the LTL classification tools that FedEx provides on their website where you can generate the classification code based on the questions it asks in the wizard. http://shipfreight.van.fedex.com/ClassificationTool.aspx