If the data is critical then just send it out for recovery.
Otherwise, you can try to fix it yourself.
Start by acquiring the exact same make and model hard drive in good working condition.
You will then need to open the bad drive and determine what is broken. You can harvest parts from the new drive to repair the broken one.
You may need to swap the platters from the old drive to a new drive.
There is a lot of information on how to do this but below is an example of the sort of work you are looking at.
https://www.youtube.com/watch?v=GZx-tU1_gOw