Nikon 21X is what in mm?

What would 21X optical (as in my Nikon l120 ) translate to a Nikon lens in MM? (as in my D3100)
and why do I think that my L120 does a better job tele-focusing?

The L120 has a 25-525mm range equivalent lens

I'm not sure what you mean by tele-focusing. The L120 has a longer lens than your kit 18-55mm (which on your D3100 acts like a 27-83mm lens)

You can try here