During a fresh installation, clicking the information icon next to the Product Key field inside the installer will sometimes launch a local text file listing common keys.
AutoCAD 2013 is a legacy version. Autodesk has moved to a subscription model, and support for activating older versions may be limited. If you encounter activation errors, you may need to contact Autodesk Support system requirements for running AutoCAD 2013 on modern versions of Windows? View your product license information - Autodesk product key of autocad 2013
If your computer is connected to the internet, follow the prompts to sign in and verify your license automatically through Autodesk's servers. During a fresh installation, clicking the information icon