there is no license in the help menu.
im using windows
It seems you installed eM Client from MS Store - this version cannot use our licenses and instead is paid via Microsoft (condition to have a version of our app on their store available).
You need to install eM Client from our website if you want to use our licenses - https://www.emclient.com
If you have data in the MS Store version, you can use Menu>Backup to create a backup and restore it in the standalone desktop version via Menu>File>Restore.