Sorry, but if you deleted them and also deleted them from Recently Deleted, they are gone. An exception to that would be if you also had iCloud Photo Library turned on in a Mac and have a backup of that Mac from when the photos were on it, or if you have them synced to iCloud For Windows on a Windows PC.
Also, iCloud Backup does not backup photos from a device where iCloud Photo Library is turned on -- i.e., the photos are not on iCloud twice, as part of both iCloud Photo Library and iCloud Backup.
iCloud Photo Library is a syncing service. Any photo you delete from a device where iCloud Photo Library is turned on will also be deleted from iCloud and from any other device connected to that iCloud Photo Library. You can potentially reduce the storage space required on a device by turning on Optimize Storage. See: iCloud Photo Library - Apple Support
Apple does not currently offer cloud-only storage for photos. If that is what you want or need, you may want to explore 3rd party options such as Google Photos or Dropbox.