Please refer below link, i think below blog can help you with steps but you can do it in your local machine and not on cloud environment
Kindly check the Restore a Backup Locally Mendix Doc to connect postgres with Mendix
Hope it helps!!!
You do not have access to your application's database on mendix, update, delete records directly, what you can do is download a backup of your database, restore it to your local machine, make the desired changes, create a new one backup, and restore this new backup to your mendix cloud environment.