Does Nikon D3100 have autofocus motor?

Does Nikon D3100 have autofocus motor?

Added (1). If i put Nikon 50mm f/1.8 D on D3100, will I have autofocus?

No. All the sub $1, 000 Nikon bodies rely on using the ultra fast AF-S, in lens auto-focus motors found in almost all new Nikkor lenses. To use legacy AF lenses, you will need to buy a more advanced camera body like the D90 or better the D7000

Only the more expensive Nikon AF-S lenses will auto focus on your D3100 because they have a focusing motor in the lens. The camera does not have a focusing motor. Just be patient and wait about a month and the new Nikon AF-S 50mm f1.8 will be available. It should cost about $80 to $90 more than the Nikon AF 50mm f1.8 but at least it will auto focus on your camera.

The D3100 has no focusing motor. The 50mm f/1.8D won't auto focus on D3100. The AF-S version of the 50mm F/1.8 is coming soon. Just wait for a couple of months.