Your local database and your free node which has a postgres database have nothing to do with each other (other then they use the same Mendix model). See documentation here: https://docs.mendix.com/developerportal/operate/restore-backup-locally and here https://docs.mendix.com/developerportal/operate/restore-backup
So either upload the cloud with your local database or if you want the cloud database again on your local machine do a restore on your local machine.
I always forget that the upload functionality can not be used for free apps. You could try to upload your data to the cloud with an Excel import or create a webservice to transfer your local data to the free node.