I don’t know how to explain this because its the first time it happened. When I plug my Ext.HD to obtain pictures I can’t access it. It doesn’t show in Finder usually it does when I plug it in now it doesn’t I tried to use the Disk Utility and its there now I click verify disk and it says “Error: This disk needs to be repaired. Click the repair disk” I clicked that last night and its still running should I continue this or discontinue it what should I do? IM a newbie in this stuff please explain in newbie terms 
thank you!
the repair is done " Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files." how do i backup whats inside the drive if i cant open it? thank you for helping me!
i think i fixed it using the Disk Utility & Clicking Repair Disk.
