After helping the old lady find the menu, he will thank you and say that you must choose not to give you good things. Then she will insist on giving it, but you still don't want it, so he will tell you that there is a sword in the backyard well. When you come out of the house, you will see a well behind the house. Putting the mouse on it will change into the shape of a hand. Just click on it.

If you choose the first two options, then she will tell you that the treasure is in the backyard, and of course you can't find the sword.