Your valid serial number is located on the outside of the product packaging or in the Autodesk Upgrade and Licensing Information email you received if you downloaded your product.
When you register and activate your product, you are asked for the product serial number, which is automatically entered upon completion of the activation process.
If you have a multi-product bundle of software that uses a single serial number, only the first product you register and activate displays the updated serial number. For other products to display the serial number, you must update it from the Help menu.
The serial number is located on the outside of the product packaging or in the Autodesk Upgrade and Licensing Information email you received if you downloaded your product.