Doraemon: Nobita and the Kingdom of Clouds (1992)

Nobita, after wondering if Heaven truly exists, asks for Doraemon to take him there. When his robot pal suggests that they make their own Heaven, Nobita enlists Shizuka, Gian, and Suneo to help, but a war breaks out between two islands in the clouds that could have terrible environmental consequences if Nobita and Doraemon don't bring peace in time!