Ngerulmud is the capital of Palau – it's situated in Melekoek State which is presumably where the confusion comes from. Some sources give Melekoek as the capital, though the most often quoted of those (Britannica.com) does so in the heading, but not in the main text which states (correctly, I think) that 'Ngerulmud, the site of the country's capital, is in Melekoek state.')