Unless we have a backup but at the top of this forum is:
This has free, free to try and progresses to data recovery houses.
The way to get your data back is to have a few backup copies. Most folk learn this the hard way.
And no, there is no one app for this work. Why? Because there is no single reason for the failure.
I was using my hard drive and it suddenly crashed. Now, the computer is saying I must format it before I can be able to access it. Is there any way of getting the data back - it is quite important? I still haven't formatted it.