Steps I followed to move my SharePoint (WSS v3) Content Databases to SharePoint 2010 on another server (including upgrade) were:-
- Detach DB from SQL2008 on original server using SQL Management Studio.
- Copy the .mdf and .ldf files for the content database to the DB folder on the new server.
- Attach DB to new SQL 2008 R2 server using SQL Management Studio.
- Create web application in SharePoint 2010 Central Administration using the same URL as the original site (must be exact name).
- After the site has been created successfully, delete its default content database from SharePoint Central Administration.
- Copy the SSL certificate (including private key) from the original server to the new server and import into the Certificates/Local Computer store.
- Configure the IIS Bindings (IP Address, SSL, Host Headers, Ports) for the new SharePoint web site.
- Run the powershell command from the SharePoint Management Shell to attach the DB to the web application in SharePoint 2010. This process also upgrades the database. ( Mount-SPContentDatabase -Name STS_<name>_848357356 -DatabaseServer <servername> -WebApplication https://sp.<domain>.com/ -Updateuserexperience )
- Configure the correct Alternate Access Mappings (AAM) for the site in SharePoint Central Administration.
- Change the Web Publishing Rule on the TMG server to point to the new SharePoint server.