I hope I have posted my problem in the right section of this forum.
I have a WD 1TB hard drive that is fairly good. However, the problems occurred when I was trying to transfer data a couple days ago. After plunging it to my PC, a message always popped up and asked me to format it. I had never encountered this problem before. All the inner data also became inaccessible. But, I did not remember I had done something wrong. Help me, please. I need to access my inner data.
Any help would be greatly appreciated.
Thank you.

it would seem this is not the case. you can make no assumptions about drives as to their "goodness" This is a cosmetic mistake, but not relevant to your issue.

1st question: Did you follow the advice of windows and do the format, or even attempt it?

There are a number of reasons why this could have happened, and really we cannot help more without more information. is this drive USB2.0 or 3? What is the model and have you tried a different cable? Have you tried using a booster power USB cable?

Does it make any strange/unusual/different than new noises? can you notice an black or burnt parts on the circuit board (if you have cracked open the case)

If your data is important, You would be best to take it to someone experienced. You can start at your local computer shop, and stress that they not do anything without your permission, such as taking the cover off to have a look or other horror stories in-the-making.

sorry, it is a can of worms, and youve opened it.

Dont see whether its an internal drive or an external USB drive.

If you have hardware issues (clicking, buzzing or other strange sounds) or even as you stated
and you have valuable data on the drive - you should not try to solve the problem on your own,
it might cause more issues and more or complete data loss - and/or much, much higher recovery
costs.

The more you (re)try (access) the drive the higher the risks.

Best advice: Ask / look for a professional DR expert in your area - my collegues here in the forum
certainly could name you one or more.....

To check the status is usually for free or for a low price - and you are secure with your data !

+++

That's why I asked if the OP had tried to format it, because a lot of people actually do it and further hinder their chances of recovery