All the usual:
Is it seen in BIOS? In Device Manager? In Disk Manager?
Can you remove the drive and put it into a desktop, connected to the motherboard without the USB interface?
Download and run a utility such as Recuva or Easeus Partition Recovery to see if the partition information got corrupted and can be recovered.
If you dropped the drive recently, it may be unusable. I'm not being sarcastic. Recently, I've seen a few "I dropped my drive and it makes a screeching noise now" posts.