The current version of the Cloud Migration Assistant for Confluence it is not supported for Confluence Data Center and this makes it very difficult for Data Center customers to migrate to Atlassian cloud.
It will be great for customers to be able to use Cloud Migration Assistant for Confluence also for Data Center.
- Upgrade the Data Center confluence version to 6.14 (or higher)
- Manually export/import the spaces
- Take a site backup and restore to save version Confluence Server (which should be 5.10.x or above)
- Use Cloud Migration Assistant for Confluence on Confluence Server to migrate spaces to Cloud