If the files have been stored on the internal storage, then the photo recovery is not possible. Additionally, if the files were stored on an external storage (SD card) then you need to unplug the SD card and attach it to a computer through a card reader or just connect the phone with a USB cable and then use a recovery solution (Recuva) to scan for the deleted files. Recuva is free to use and it has good accuracy for scanning image files.