What are the best camera settings for shooting in dark?

Flash on.                              !

Which camera are you using since not all cameras have the same settings available let alone the same level of capabilities?

There are no universally "best" settings for shooting in the dark.  By the way, how dark is dark?  Are we talking about being inside a house, a gym or outside at midnight?  What are you photographing?  Do you need to stop motion?  If you're shooting people, you'll need to use a shutter speed that will prevent them from being blurry due to their movement.  If you're shooting a landscape, then shutter speed isn't a concern unless you're not using a tripod, which you should do in this kind of shooting situation.  With a landscape your depth of field is critical and will likely need a small aperture which could mean that your shutter speeds could be 30 seconds or longer.  If that's the case, then you'd need to be in Bulb mode which allows for shutter speeds longer than 30 secs.

The "best" settings depend upon what you're photographing and what kind of depth of field you need.  For most situations, just put the camera into Auto until you understand how the aperture and shutter speeds affect the look of the image.

Look up the exposure triangle - it still applies to low light conditions.  Exactly what settings you need will depend on what you're trying to photograph, how much light's available and, to some extent, how your camera performs in low light and what sort of style you're after.

You CAN'T shoot in the dark.

If there's some kind of light around, you can up your ISO (at the expense of image quality) stick your camera on a tripod, and/or - if you're close enough - use flash.

NOBODY can tell you, "ISO x, shutter speed y, and aperture z," for a given situation, because there are too many variables.

In absolute dark, there are no settings that will work.

In extremely low light, wide-open aperture and very slow shutter speed,

or a smaller aperture and an even slower shutter speed.

Often enough, an exposure time of several minutes to several hours

may be called for.

This demands the use of a tripod or other suitable support.