Do 2.5" SATA HDDs in an external enclosure need extra power over USB with Windows?
What is the exact make and model of external enclosure you are using? Some of them require an external AC adaptor. Some of them come with a duplex (two-headed) USB cable and require that both of them be plugged in to powered USB sources to provide enough voltage to run the enclosure and the drive.

Of course it is possible that your hard drive itself is damaged. If that is the case, you will need to pay a lot of money to a specialty hard disk data recovery service.

Finally, do you not already have a Time Machine backup of your Mac's internal hard drive to an external disk drive? When this current situation is resolved, it would be wise to invest in an external backup system using Time Machine.

UPDATE:

Have you tried this drive in a different external enclosure? until you do that, you can't rule out that it's the external enclosure's problem and not the drive's problem.