On the cli type "license export <file name>". This will create a file in flash with the name you provided. That file can be copied off the controller via FTP or TFTP and can be copied back down and loaded using the command "license import <file name>".
Also, if you use the command "backup flash" that copies everything (configs, database, licenses, etc.) into a single file called "flashbackup.tar.gz" that can be used to quickly recover a box.
You can also find your licenses online via the License Management System: https://licensing.arubanetworks.com/