If all other troubleshooting fails,, then here is recovery info.
If you do not know what you are doing and do not want to further compromise your data, you are better taking this to a professional.
A very good recovery tool for partition recovery is called
TestDisk
This is not a point and click software, it is DOS menu driven, but, it works very well if the partition is recoverable. But, you can also destroy data if you are not careful using this software and follow the help. I have found, that if TestDisk can't do it, there is not much else that can, for do-it-yourself recovery.
The only other software that I would recommend if for some reason TestDisk doesn't work, or you don't like it, is,,,
SEAGATE FILE RECOVERY , This is very good software for recovery and you can download the trial and run it to see what it finds before buying it. You can recover small files to make sure it is working and that not all the data is corrupted. File recovery methods, techniques and instructions would go far beyond a simple post, so........
If neither of these work to recover the data, then it is most likely gone. Or the drive is damaged and can not be recovered. You can send it into a place like Seagate Data Recovery service and see what they can find, but it is not cheap. Or continue trying many other recovery software, but......
Or if the files have simply been deleted
SoftPerfect File Recovery is excellent.