Not sure if by Express he means SQL Compact. The free version of SQL server is SQL Server Express, which is limited to 10GB.
Regardless, if it was compact you can use Jacob's link. Otherwise, its just a simply back up and restore operation DB wise.
You can follow this KB to move your database: https://www.lansweeper.com/knowledgebase/moving-your-database-to-a-different-server/
It's up to you if you also have your scanning server on the DB server or if you use the current server for both the service and the website. Safest thing would be to just take a backup, remove Lansweeper, and reinstall just the components you need.
After that you just have to link them together by connecting them all to the DB.