This links to the search results that I was presented with, and will open an image of different Genesis plugs.
As I don't know if yours is round, trapezoid, etc.
Hopefully this link will help you narrow it down for you.
https://duckduckgo.com/?q=Sega+Genesis+16+bit+A%2FV+Cord+pin+out&iar=images&iax=images&ia=images&iai=http%3A%2F%2Fi246.photobucket.com%2Falbums%2Fgg91%2Fmajorfatboy%2FAmiga1080_to_sega_01A.png