How to merge or combine faces into one surface

I’m having trouble combining 3 surfaces into one surface so that I can extract one bounding edge of he entire surfaces but all the components I have tried including brep join, solid union, region union, etc., are failing. I know the edges are messy but I don’t min that and from what I understand it shouldn’t be causing an issue. Any help would be much appreciated.
merge faces (40.2 KB)

merge faces (45.6 KB)


wow!! amazing thank you!!