MY PASSPORT 4TB- Back up data not showing up

Backup data(which gets automatically updated when connected to my laptop) stored on my external 4TB hard drive is not showing up.It is still there as i can see the space used (around 450gb) but is just not visible.Other data which is stored on it is totally accessible but backup data is not showing up.All the backup data was in the folder named 'WD Backup.swstor…cant remember whole name.The folder is missing.No folders are hidden on my laptop.
While scanning for errors through windows it shows no errors but if i run 3 tests provided by WD Utilities,it passes the first one(smart test) but fails in other two(quick drive and complete drive test).
Hourly back up(which i have paused for now) starts backing up from scratch which i think shows that device is not able to recognize that that there is already 450gb data in there.
what to do?

In my case,as i mentioned above,other than back up data everything stored on hard drive is accessible.
kindly HELP.