Quintillion is 1 followed by 18 zeros. So it would be
200.000.000.000.000.000.000 tons
That multiplied by 1.000 (1t=1.000kg) you'll get how much kilos he can lift. Its basically the same number with additional 3 zeros:
200.000.000.000.000.000.000.000 kg
Simplified, that's 2 x 10^21 kg, which is about 1/30 of Earth's mass, which is a joke to what Superman can actually lift.

He was able to hold a miniature Black Hole in his hands in an issue of JLA volume 3. A small Black Hole weights around 5-10 times than our Sun. Our Sun weights around 332.000 times the mass of the Earth. Let's say he was holding a very small Back Hole, 3 times the weight of our Sun. That's 332.000 times 3 is 1.000.000 Earths (rounded). Earth weights:
5.974.200.000.000.000.000.000.000 kg
times 1.000.000 equals
5.974.200.000.000.000.000.000.000.000.000 kg
Now thats sounds about right, doesn't it? Its superman after all
