It is almost certain that your hard drive is damaged.
The first thing you should do is download and run diagnostics from the hard drive manufacturer. Start with the simplest, quickest version first.
If it's damaged, but still functional you may be able to recover your data. The only tool I found for my 2TB Western Digital which was unrecognized was the (not free) program called "EASEUS DATA RECOVERY WIZARD"; I tried more than 10 programs and it was the ONLY one that worked.
You may have to have another hard drive to copy the data too.
Basically, when your hard drive dropped the shock may have damaged the part that indexes your hard drive and knows where everything is. However, if the hard drive is sufficiently functional (even if it never works properly again), it may work well enough to scan every single part of your hard drive and recover the files.
EASEUS works something like this:
1) start scanning at beginning of drive
2) Looking for the last part of every file, for example an MP3 audio file ends with ".mp3"
3) when it finds this combination of characters it jumps backwards to find the beginning then flags it
I believe it takes roughly 6 hours for 1TB of data.
The setup probably looks like this:
1) add this drive to a working computer
2) have another drive (can be USB) to copy files too. Must be large enough for all your files (if you had a 2TB drive and it was less than half full you need 1TB of space or less)
3) start EASEUS (recommend the highest level of scanning. Scan for everything)
4) EASEUS, if possible, finds the files then copies them to the other drive
*you can always try formatting and running diagnostics on the drive after this. It may still work.
**NEW HARD DRIVES:
Always do this:
1) FORMAT, then
2) CHECKDISK-> Scan for bad sectors
Scanning for bad sectors checks the entire hard drive and creates a list of spots, if any, that are not writeable. You must do this BEFORE you write data or else you can get corrupted data.
A "full format" is the same as Format+Bad sector checking. A quick format creates the index tables (formats) but does not check the hard drive for errors.