I dropped the grandson's external drive.
If the hard drive itself is damaged, recovery of any data on it may only be possible by sending it to a business specializing in such.
I'd suggest opening the case of the unit, and you should find that the drive in it is what is in a desktop or laptop computer, with the appropriate electronics to adapt it to USB. There will be at least one cable connection to the drive- make sure it is properly seated. I've seen an instance where the only problem was a partially disconnected cable.
Another possibility, is, if it is a standard drive, to let a tech savvy person take the drive itself, and connect it to a standard computer, and see if it is then readable. If so, data can be recovered.