Upgrading as an Existing User with access code

Hello,
I have an existing free account associated with my university email address.
Recently my university has purchased licences for all students and now I am trying to upgrade my account using the code I received from my university.
I followed the instruction for upgrading as an exiting user, but the menu I see is different - no "upgrade account" option under the account setting (see screenshot attached) .
I would appreciate your help on how I can use the code to upgrade my account
Thanks!