When you delete the photos from a device while it is syncing with iCloud Photos, it will delete the photos from iCloud and all other devices as well. You can recover the photos from the Recently Deleted album within 30 days, after you deleted them, unless you also emptied Recently Deleted.
If the photos are gone from Recently Deleted as well, you have to use the backups you made, while you still had your photos. You need to use a backup you made on a computer, as your regular iCloud backups of your iPhone will not have saved your photos, since you have been using iCloud Photos. If you have a backup on your computer, restore the iPhone from the backup to recover the photos. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support