How to combine 2 folders to new folder?

[london7871]

How to combine 2 folders to new folder?

Existing folders and filenames:
Existing folder "AA": AAA-001, AAA-002, … AAA-015
Existing folder "BB": AAA-002, AAA-002a, AAA-016

Output:
New folder "AA+BB": AAA-001, AAA-002, AAA-002a, … AAA-015, AAA-016

Pls note file in "BB" replace that in "AA" with same filename. (e.g. output AAA-002 is from "BB")
Enclose with folders "AA" and "BB" for reference.