Alma and Helaman established churches before the coming of Christ. They were covenant churches related to those that Alma the Elder established when he brought together the people who had been baptized at the Waters of Mormon. When they arrived in Zarahemla, Alma the Elder obtained a special decree from King Mosiah for them to live in separate covenant communities; they called them churches. The word for church in both Hebrew and Greek means a gathering or a collection, a community. There were seven of these churches in Alma the Elder’s day.
Alma the Younger established similar covenant communities in various cities, and his son Helaman continued the same activity. While these may not have been churches exactly in our modern manner, they were organizations that encouraged people to keep their covenants. Perhaps they were more akin to what the ancient Jews called a synagogue, a house of scripture reading and prayer and community concern and celebrations.
The Book of Mormon gives us something that is not in the Bible, namely records of the transition of a group of Israelite people, who started out in Jerusalem and developed over six hundred years. There were covenantal changes with King Benjamin, and organizational changes under Alma, and finally they were prepared as a people for the Savior to come and institute such things as the administration of the sacrament by twelve appointed disciples. In the Book of Mormon, the church can be seen emerging, unlike in the Bible, where nothing is contained for the years between Daniel and the birth of Jesus.
Book of Mormon Central, “Why Did Alma and Amulek Preach in Synagogues? (Alma 16:13),” KnoWhy 124 (June 17, 2016).