My developer has asked me to provide an api key so that they can upgrade our version of civiCRM and set up cron and mailing system. I have no idea how to do this....
the API key sits in the database as a field for the CiviCRM contact. You can find it in the table civicrm_contact.
If you are not too technical and do not access your database directly on a regular basis the is an extension you can use called API Key (https://civicrm.org/extensions/api-key) which will show an additional tab for contacts if you are a sysadmin where you can see and add the API key for that user.
Does that answer your question?