How much energy would be required to melt enough ice to give 2 litres of drinking water if the?

Energy is not a physical unit. It is a philosophical concept and an accounting technique used to analyze mechanical and chemical exchanges. In nuclear physics it is defined as a wavelength of light, in biology it is a synonym for metabolism, and in public utilities they say energy when they mean connectivity. Anybody who uses the word in any other context either does not know what he is talking about, or is peddling something you don't need. The word you want is heat, and the answer is simple arithmetic: 2000 x 333.35 = 666,700 joules.