If you had iCloud Photo Library turned on before you lost the phone, you can use a computer and go to the Photos app at https://www.icloud.com/ and view and download the photos from there,
If you didn't have iCloud Photo Library turned on but had the phone set to automatically back up to iCloud, you cannot view the photos via iCloud but you can use the iCloud backup to restore to a new iPhone.
If none of the above, you may want to contact customer support for iBackupExtractor https://www.wideanglesoftware.com/support/ to see if they can help.