Check under the hood, but maybe hard to locate if it has a cover over it. You might be better off to look in that area from underneath. You are looking for a tank, about 5-6 inches in diameter and about 18 inches tall with a drain plug on the bottom. The filler cap will be on top accessed from under the hood.
John & Clare Lyon
2007 43.5' Monaco Dynasty Palace III (All Electric)
Towd: 2011 Chevy Equinox