...
To migrate specific projects or repositories, we recommend cleaning up Bitbucket first by removing any unwanted projects or repos and using the standard Bitbucket front-end (or the Bitbucket REST API for teams that are comfortable scripting). Once your Bitbucket server has only the projects and repositories you want, use a standard Bitbucket migration process to migrate the Bitbucket data. This is the safest and most straightforward migration approach when to combining migration and cleanup tasks.
...