how can I fix my 2T External hard drive?

In the cmd run the following commands.

To use the command line to bring a disk online, create a partition, and format it, run the following commands:
 C:\> Diskpart
DISKPART> list disk
DISKPART> select disk (id)
DISKPART> online disk (if the disk is not online)
DISKPART> attributes disk clear readonly
DISKPART> clean
DISKPART> convert mbr (or gpt)
DISKPART> create partition primary
DISKPART> select part 1
DISKPART> active (if this is the boot partition)
DISKPART> format fs=ntfs label=(name) quick
DISKPART> assign letter (letter)
DISKPART> list volume

This will make the external drive useable again. Just a note, you run the commands after the '>', and some of them may a bit to complete so be patient but it shouldn't take too long. The longest part is while it detects your drive. It will detect it though. also i have attached a doc for you to view to assist you with this.
Format-Disk-from-CMD-using-Diskpart.docx

Nothing wrong with trying the steps mentioned above, but it sounds as if the drive or enclosure electronics are not working properly.  Did you initialize and partition the disk before trying to format it?

why it tells that the drive is not recognized as internal or external command?

Yes, I partitioned it but after I partitioned it becomes RAW and can't complete the format.

did you try the instructions

Yes

At a guess CompProbSolv is correct.

Now as an end user you probably can't or don't want to do this, but here's what I would do if it was on my bench:

Open the drive enclosure.  Have a look at the drive.  If it's standard IDE or SATA, remove the drive from the enclosure and test the drive directly using a motherboard drive port.

If it works there, then the external enclosure's USB controller has failed; throw the whole enclosure away and buy a replacement one on fleabay.  If it doesn't work there, then the drive itself is faulty and it's either pack it off to a data recovery company or toss the drive out.

I'd concur with Dr. Klahn.

My presumption from the fact that you're trying to format it is that it doesn't have any data on it of importance.  If you can deal with a bare drive, disassemble it as he suggests.  You risk breaking the case, but it's of no value to you at this point anyway.

what model drive is this?
does it have a separate power supply? if not, test it with a powered usb hub
if you can, switch the usb cable too
post a screenshot of disk manager too