I think that examples of the mood in Lamb to Slaughter were:
Suspense- You were wondering whether or not she would get caught
Mystery- There was a mystery, after she covered up how she murdered him
Anticipation- You were waiting for them to realize that she could have killed him with the lamb that they were eating.
The mood in "Lamb to the Slaughter" shifts from tension and shock to dark humor and irony. It begins with a sense of unease and disbelief, then turns to a more macabre and ironic tone as the story unfolds.
happy and sad
The setting of the story does this.
A story has one overall mood, but within that mood, it can have several changes. For example, a horror story's mood would have to be horror, but there can be humorous or even romantic scenes during the course of the story. The mood can even change over time, from one thing at the beginning to another at the end. However, you usually consider the overall mood when you're describing that for a story.
the mood in the story is jealousy
Mood can be set in several ways. You can show the emotions of the characters. You can also use setting to show a specific mood (for example, setting a spooky story at a scary old house) or to emphasize an opposite mood (for example, setting a scary story at a fun park).
The setting can either reinforce the mood by appearing as the reader expects it to (for example, a spooky old house in a scary story or a bright seaside in a romance), or it can emphasize the mood by seeming to be "opposite" of what's expected (for example, a horror story set in an amusement park or a romance set in outer space).
what is the mood in a story
Interesting is not a mood, so no. Interesting would be your opinion of the story, but it's not a mood.
The conflict helps to tell the mood, but it's not the only thing. Mood can be created in many ways. The words that the author chooses - their style - is a major contributor to mood. Words like dark, dismal, spooky, eerie, or isolated might create a scary mood, for example. Setting can also help with mood. A romance story set in a spooky abandoned warehouse might not have the right mood.
The mood in a story is something that can be set throughout a story. At any moment it can change as well. The mood can go from bemusing to frightened to amused. All in the span of a few pages. As the author you decide the mood for a story and how you change it depends on your story. Of course in setting a mood or changing it, of course it must make sense.
the mood of that story is sad and the tone are also sad