In pgadmin, rightclick the name of you database and in the contextmenu that shows up, select ‘Backup’. That will export the data to a file. This is “database only” by definition, since you have created it using a “database only” download.
Then go to your project in sprintr and click “Backup”. Then click “Upload Backup” and select your file. Pretty sure it will get accepted as a valid file for restore as long as you have only removed objects.
Mind you: if you cleaned up objects the refer to filedocuments, those filedocuments will become orphans that will keep taking up space on your storage.
See for more info: https://docs.mendix.com/developerportal/operate/backups#3-2-1-uploading-data-in-mendix-cloud-v4