I have connected an external storage device to my new MacBook pro but the operating system isn't recognizing the device's cont

[shelshel]

Connecting an external storage device to my new MacBook pro but the operating system isn't recognizing the device's contents. It asks whether I want to format the device. Why might this be happening?

 

[rgd1101]

the device was formatted in a file system that the Mac don't understand. Did you use the device somewhere else?