1.Stop using your SD card right now in case of overwriting, which could make your original photos gone permanently.
2. Apply a memory card recovery programs to help. In fact, if you search the word"data recovery program", you can get a piles of recovery programs. You are supposed to select some good and efficient one. If you also hava no idea about it, you could read this text fist and then make your decision:
3. Store your data on the right place. You should save the restored photos on another memory card for the safety of them.