Once you've found him, you can talk to him and ask for a fish for Margaret. He might require you to do a small task for him before giving you the fish, but it's a simple request.
Good luck on your fishing quest!
Where do you find Hank the fisherman to get Margarets fish in MySims Kingdom?
You can find Hank the fisherman on the beach in the north-eastern part of the kingdom. He's usually fishing from a little dock, and you can easily spot him thanks to his bright orange fishing rod.