Hukam is the Divine order or command in Gurbani. It is broader than a single instruction: Japji Sahib invites the listener to live in alignment with Hukam rather than centring the self. See Sri Guru Granth Sahib Ji, Ang 1. A Hukamnama is the particular passage received from the Guru Granth Sahib; it is not another name for the whole concept of Hukam.