Other contributors have said "How do you Japan in Japanes?" is the same question as "How do you say Japan in Japanese?" If you believe that these are not asking the same thing and should be answered differently, click here
日本 reads both /ni hon/ and less formally / ni-ppon/, which means 'Japan' in Japanese. 日本国 /ni hon ko ku/ literally means 'the country of Japan', which is also another way of saying the same thing.