The Migration folder is a public folder that is created automatically by WPvivid Backup Pro on your cloud storage. It is located under the custom parent folder(by default ../wpvividbackuppro/) you created when authenticating the cloud storage.
This folder will hold the backup of a website that you want to migrate. Then on each website you have authenticated to this storage on, you can access the folder and the backups inside, which means you can easily download a backup and restore it to a new destination site or a new domain.
Note: You have to delete the backup manually when you do not need them anymore.