First of all, you have to read the short story for several times, then read about modernism and postmodernism literature....
later on , you can fegure out the coventions that characterize the phase and the story yourself ........
Postmodern Literature Defined
Postmodern literature is a form of literature which is marked, both stylistically and ideologically, by a reliance on such literary conventions as fragmentation, paradox, unreliable narrators, often unrealistic and downright impossible plots, games, parody, paranoia, dark humor and authorial self-reference.
Postmodern authors tend to reject outright meanings in their novels, stories and poems, and, instead, highlight and celebrate the possibility of multiple meanings, or a complete lack of meaning, within a single literary work.
Postmodern literature also often rejects the boundaries between 'high' and 'low' forms of art and literature, as well as the distinctions between different genres and forms of writing and storytelling. Here are some examples of stylistic techniques that are often used in postmodern literature: