When Studio Projects were introduced many years ago in CMS 8 (7.1.10) and DXP 8 (7.5.34), they replaced a feature called Content Sets. The Content Sets feature was removed at that time, and data was automatically migrated to Projects. This automatic migration has been removed with this release.

If you still need to migrate ancient Content Set data, then you have to upgrade to a previous release first, and start the Studio Server once to migrate the data. The Studio Server of previous releases logs this data migration during startup with INFO message "Converted ... content sets to projects".

(CMS-7389)