You can try below troubleshooting steps to recover your files :
1.) download the Android phone number recovery tool in your computer.
2.) Install and run the Android phone number recovery tool and after it will ask you to connect your device.
3.) Connect your phone to the computer using a USB port.
4.) Enable USB debugging in your settings.
-if the android version of your phone is Android 4.2 or newer: go to Settings > About Phone >Build number > tap for several times until getting a note "You are under developer mode" > Back to Settings > Developer options > Check USB debugging
- if your android version is Android 3.0 to 4.1: Settings> developer options > USB debugging
- if the android version of your phone is Android 2.3 or earlier: Settings > Applications > Development > Check USB debugging
6.) After clicking next, it will prompt you to choose what data you want to recover. Choose Contacts
7.) Hit the Next button
8.) When you get a superuser window, check your phone and hit ALLOW to allow recovery then hit START in the application.
9.) After that you will see your recovered contacts. You can transfer all your contacts using the ANDROID TRANSFER that you can also install in your computer.
hope that this will help you in retrieving your files!