what does a male nanday conure look like?
Both the males and the females look the same. There is no way of telling them apart by just looking at them. You would have to have your bird either surgically sexed or have a DNA test done. The DNA test is a lot less painful for the birds, by the way.
There are some exotic birds that you can tell what sex they are by just looking at them. For example, the eclectus, the females are red and the males are green. But as far as the Nanday Conure, there are no visual cues that we humans can see without doing one of the two tests.