f you purchased MATLAB Student License, then your Activation Key would have been emailed to you. If it was not, then contact sales@mathworks.com or call Mathworks for free installation support.
If you purchased any other kind of MATLAB license then those would use license numbers rather than activation keys.
If you are using an license supplied by an organization, including licenses supplied by universities, then they are responsible for providing you with the necessary keys.
None of the volunteers here have access to the license database, so we cannot even check to see if a key is license is registered for your account.
