how do i retrieve data from my external hard drive?

May you please elaborate?

Connect it up to the USB port and open the Finder window. The drive will be listed in the left hand pane. It may also show as an icon on the desktop.

If your hard drive can be detected and shows up as a drive letter in my computer but you can't access your files,then you can recover your data off it with data recovery software easily.This way is the easiest and the most inexpensive way to recover your data.If you bring it to a computer repair shop that is available for data recovery servise,they will cost you $500-1000 or more.Hmm, a lot of money.

I managed to recover data from crashed hard drive with Tenorshare Data Recovery.If needed,you can download it and scan your hard drive for free to preview whether your data can be recovered.It will show you thumbnails for recoverable pictures.

Data Recovery from an external drive is possbile try to find any good recovery software from the forum or check these below given software.

Stellar Phoenix Mac

Data Rescue
Disk Utility
Disk Warrior
Drive Genius
File Recovery for Mac
TechTool
R3Cover

FileSalvage