What settings do i put my nikon d3100 on to film in slow motion?

What settings do i put my nikon d3100 on to film in slow motion?

You set it aside and get a camera that has that ability. The D3100 does not.

You need to film at least 60 fps to get slow motion. Your Nikon only shoots at 24-30fps, so you can't get slow motion with it. You should have bought a Pentax K50 which can shoot at 60 fps if you're doing a lot of videos.

Film in regular speed. No way to change it. It's not a video camera, right?

Adjust playback speed in the computer using a video editor.