A.) Permanent marker, write plug # on side of molex connector and never accidentally mix things up again.
B.) Download the manual and look at the wiring matrix. It tells you exactly where the wires connect in the back box.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.arcade-museum.com/manuals-pinball/F/Funhouse_OPS.pdf&ved=2ahUKEwjKnayQ_ZfkAhXCIjQIHWqPB7UQFjADegQIAhAB&usg=AOvVaw38zj1DBTtzozOf9RaAZNVq
C.) Other issues visit https://pinwiki.com