It is not possible to upgrade from ISPmanager Lite (Pro, Host) to ISPmanager Business on the same server. You have to install a new server for ISPmanager Business because the products have different architecture and software applications.
We strongly recommend a clean install of ISPmanager Business on a new server. Then you can import user data.
For more information please refer to the article How to move ISPmanager from one server to another.