We currently do not provide any official migration tools to fully migrate the TeamSpeak 3 database towards TeamSpeak 6.
However as of writing we recommend using the Client snapshot feature which was recently released, it copys the most important settings and allows for customization by manually editing the .json file:
To get started right click the server and click Server Snapshots
The following approach is not supported and not endorsed by us.
It is technically possible to partially migrate certain elements, such as channels and groups, by modifying the database.
However, we do not recommend or endorse this approach. Please note that performing such modifications is entirely at your own risk and we will offer any support if you are experiencing issues due to the migration.