At any time upon passage of this chapter and said chapter becoming law, any Class 5 municipality may adopt the mayor/commission/city manager form of government by adopting an ordinance by a majority vote of the members of that governing body adopting the mayor/commission/city manager form of government. Within 30 days of the adoption of the ordinance adopting the mayor/commission/city manager form of government, members of that governing body shall adopt a second ordinance for the election of commissioners from six single-member districts with the district boundaries established therein.