I didn't work I guess.

I didn't work I guess.

Am I too sleep dep for the helpdesk right now....
sudo chown raaghu:raaghu '/mnt/a9d058e3-c98d-49ba-80b5-51a2fb3537b8/dev/sda3'
Please don't mind!

Maybe I am too hung up on thinking of the /dev/sda3...
sudo chown raaghu:raaghu '/mnt/a9d058e3-c98d-49ba-80b5-51a2fb3537b'
This should be easy - I have solved this in one post a dozen times. I am stumped.
Oh!! I normally I encounter special problems!
Is there a way out?
I am sure there is and that it will be easy.
I seem to be failing you right now.
What is the output of
sudo nano /etc/fstab
Well, I see where I went wrong in the /mnt/a9d.... that would try to mount the mount point, not the drive. That makes sense.
However, that /dev/sda3 is not responding is what has me stumped.
Are you able to see the files in your File Manager and access them? But just cannot write within?
Yes, it was the case earlier. That is, before we started trying to solve. But now it is not the case. When I am trying to open Partition D, I get the following error.

At this point, I think you should run fsck:
Okay, let me try and get back to you.
Hope you will be available. If not please try to respond when you get time.
Thanks.
I noticed user #999 is shown as the owner of this partition.
I vaguely remember I saw it when I was installing MariaDB.
Do you have mySQL installed on this system by any chance?
Hi guys,
I tried the link but didn't work out much.
So, I did format the partition and then changing the process of changing the ownership worked after that.
Thanks a lot for your time.

No, this was the first time.
And do you have any mySQL?
Yes, uuid 999 is the Live USB / Live CD Zorin...
I had not even noticed that in the O.P.'s screenshot. 
I was paying all of my attention to the First Screenshot showing the disks and whether it was mounted.
Talk about a facepalm... No wonder the command did not work - If he was booted on the LiveUSB.
More often than not, clean installation solves much problems.
Thanks for this information.
I did not know that.
I think I noticed it just because I recently installed LAMP stack from command line only. This kind memory is way more persistent than GUI experience.