Do not format the drive.
Download Recover My Files from
www.recovermyfiles.com. Install it on your C: drive. Run a "Fast Format Recover" on your D: drive to see if it finds the files.
If a Fast Format Recover does not work (it will take about 20 minutes to run), then try a Complete Format Recover.
Click on files found in the results screen to preview the file content.
Please let us know how it goes.