how I delete a group from message on my MacBook pro?

Not sure what you mean by "group" in this context. Do you mean a "conversation"?

You can select it in the Sidebar, and drag it left until a red button with a trash can appears, then click it.

I know what you mean. On my MBP, when I want to send a message only to "Joe," a Group Name appears as well, "Joe, Diane, Larry." If I understand you correctly, you want to remove the "Group" and ONLY see Joe's name so the message goes to Joe without any chance of making a mistake and sending it to the entire group. (I don't even know how the group was started, I didn't create it.)

I don't have an answer but hopefully the Community can let both of us and others know if and how to remove the group permanently.

FYI: I just searched additional chats and see that this problem has been bothering Apple users since at least 2019.