HDD Diagnostic error code failure: 2000-0142

So my pop's pc has been acting out lately. So I ran a diagnostics test to find out what the problem was. Turns out it was a 2000-0142. I know this problem is not solvable, and the only way is that you have to buy a new HDD to resolve this. BUT, I am not sure if the HDD can still be connected as an external HDD and take the files inside it, because my pop's 8-year long documents are in there. This is really important to him and he'd like it to be working again. 

If there is any other solutions of 2000-0142 or connecting a 2000-0142'd HDD to my pc that I don't know about, please let me know and I'll try anything out to bring it back to life. 

Things I tried:

• Reset pc (said that it cannot be completed)
• Run it back to previous Win 10 Version (Cannot be completed)

So basically when Dell pc's are unsuccessful to reboot, there is a menu that pops up after 3 tries. I've tried every button in there and said that it cannot be completed. 

Thank you for your time and help.