cgsecurity.org

After a Quick Search, there had no partition listed.

It showed Key A: add partition, L: load backup, enter: to continue

I am thinking to press enter: to continue, but would like to know what will happen after I press enter?

You easily will get to the next screen!
If Quick Search didn't find something, you can run Deeper Search.
It appears at the next screen.
Can you copy and paste the content of your testdisk.log here?
You'll find it in your testdisk folder.

TestDisk doesn't change anything until you explicit confirm it at Write and y!
So TestDisk only diagnoses your Disk and displayes the results.

Thanks for your answer.

Unallocated disk problem has been solved.
After uninstalled several disk cleaning software, windows found the disk.