You want to upgrade to the new Review Apps
In Pipeline settings, go to the section for Review apps and click Upgrade this pipeline.
All your existing Review Apps will then be migrated and will still be available after the migration.
Create new Review Apps
To create new Review Apps, please make sure the required config vars are either set in the app.json or in the review app config variables in the pipeline’s settings, as explained in the Dev Center article.
PLEASE NOTE: You can not migrate back to the old version of Review Apps once you make this change.