This article shows how to migrate license between servers/sites.
View Available Licenses
Log into cloud portal and go to Subscriptions, you should be able to see all the licenses you have purchased.
Press the Disconnect button next to the license you want to re-assign, and it should be now now moved to un-used state.
Activate another site
Create a site on another/same server and start the activation process as per. Choose the license to be same as the one you have purchased.
In the next screen you should be able to choose the old license and activate it directly.