Can I use a canon zoom lens on a Nikon d3100?

Will it fit?

No. The Canon EOS mount is wider than the Nikon, so there's no compatible adapter. There are adapters that can mount a Nikon lens on a Canon body.

No. They have different mounts.

Can you use? If you can find an adapter that will make it possible. Will it fit? Not directly, again, only with an appropriate adapter. Bear in mind that if you ever find the right adapter (if it does exists) you will be using the lens in full manual mode. You might not even have the luxury of using the lightmeter.