I dropped my passport WD external hard drive on the floor. My computer does not recognize it

Have you taken the case apart? Are all the cables connected still? You should check that first as by dropping it something could have become disconnected internally.

Is the drive making a constant clicking sound? If so the drive is irreparable and a data recovery center in your area will have to take a look. Google one and inquire.

They will not be cheap.
Chances are good that it is gone to heaven.

If it is spinning up when you plug it in and no ticking sound then it might just have come loose inside. Chances are very poor of this happening.

Take it to a IT shop so that thy can check it for you. If the drive is fine they can just give you a new case and transfer the hard drive. THIS WILL VOID your warranty.

Hope this helps.
Grant