Moving Databases between Instances of different Versions of SQL Server
The best way will be to use backup-restore - using start-dbamigration .. This will take care of migrating entire instance including all databases, logins, jobs, etc.

Make sure you use -BackupRestore switch with appropriate network location 

e.g. 


  Start-DbaMigration -Source sql2016 -Destination sql2017 -BackupRestore -NetworkShare \nas\sql\migration