Adam in genesis is exactly one man. God later took "A" rib from Adam to create for him a wife. There were not a humanity's worth of ribs taken for a humanity's worth of single men.
However, the Bible does refer -in later parts of scripture- to all the descendants of one man in block or group terms. For example: "the line of Jesse", "the tribe of Benjamin", or "Judah".
The last one, Judah, refers to all the descendants of Judah. In this way, it would be acceptable to use the term "Adam" to refer to the descendants of Adam. However, Adam was originally just ONE MAN.
The idea that Adam in the beginning was more than one man is bizarre. It is impossible to derive such an idea from the scriptures. If you think back, I expect you will remember having heard this from someone else- that is how bad teachings originate. They can be traced back to those wolves scripture warns us about.
When I was in the Methodist church, I heard so many stupid and bad teachings... the UMC is under the World Council of Churches- an organization established and controlled by Satanists and devils. (Part of the coming one world church, I expect.)