Seagate External Hard Drive Eject

Seagate External Hard Drive can not read on my mac.?

Thus, a couple of weeks I spent all my photos from my Mac to an external hard drive, and that is not read. When I connect the USB cable to the Mac simply says, "remove" or "ignore". What should I do ?!?!?! I opened utility disk, but the repair disk option is not available.

Open Disk Utility and select the hard disk External and click Repair.