If you purchased a Student license then there is no associated license number -- Student licenses work with "activation codes"
If you purchased a Standard (also sometimes called "Professional" or "Commercial") license, or a Home license, then you would have been sent your license number when you made the purchase.
Meanwhile you can visit https://www.mathworks.com/mwaccount/?s_tid=gn_myac to see what license is associated with your MATLAB Answers account.
