Box 1: Upgrade TFS to the most recent RTM release.
One of the major prerequisites for migrating your Team Foundation Server database is to get your database schema version as close as possible to what is currently deployed in Azure Devops Services.
Box 2: Use the TFS Database Import Service
In Phase 3 of your migration project, you will work on upgrading your Team Foundation Server to one of the supported versions for the Database Import Service in
Azure Devops Services.