I been using this before on back-up, but when I plugged it again, it goes like this, what should I do?
BACK UP YOUR DATA NOW!!!!
Turn the machine off, go buy a USB HD if your don't have one and copy everything of value that is on the disk.
As a commenter tijybba said above, you can try formatting the drive and plugging and unplugging the drive from the motherboard (edit: I see now from the image it's connected via USB so that's probably a no-go), although it is really unlikely that this will fix the error. SMART Tests not succeeding usually means just what you would expect: the disk will be toast soon.
You might want to check which tests are failing by clicking the SMART Data button and scrolling through the list:
This answer has a good explanation of the tests and which ones are important.
Please be advised that I have never had a hard drive last for long when SMART tests began to fail. I recommend you replace with a new HD ASAP.
I hate to be telling you this, but you need a new hard drive.
Here are things that you can try: