Hi Kylie and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
I'm sorry about the loss. As you probably already know, when you delete something from your phone, only the reference to that file is being deleted and the actual file will be still there for a limited time* and could be recovered using third party data recovery applications. These deleted files will be there until they are over written with new ones. It is possible to retrieve deleted files like photos. But that completely depends up on how much you used your phone after you deleted them.
If you have taken photos or videos, downloaded apps etc after you deleted them then the chance of them getting recovered is slim to none. Because they might be over written with new ones.
The more you use the phone, the more it become hard to recover. However, you can attempt to recover them using the following applications
Dr.Fone for Android from Wondershare --> https://www.wondershare.com/data-recovery/android-data-recovery.html
EaseUs --> http://www.easeus.com/android-data-recovery-software/free-android-data-recovery.html
The application are paid ones, so try the trial versions before buying it. Again, I can't guarantee they can be recovered. If you are unable to recover them, please don't rate me bad or poor as this is something I can only give instructions on and the success completely depends up on the factors I mentioned.
Note : Using the above recovery application will result in rooting/hacking of your phone. This may void your warranty on the phone. If you don't want to lose warranty, please don't use the above applications
The recovery applications might not work if you have already update to latest Android 6.0 or 6.0.1 Marshmallow version
If you have any questions or would like any additional information, please don't hesitate to ask.