Population III stars are a theoretical population of metal-free stars that existed during the first billion years after the Big Bang. This ended the Cosmic Dark Ages. Despite theoretical advances, we still do not know how massive these first stars were, and when and how the transition to enriched star formation took place. Though the direct observational detection of Pop III stars is likely beyond the reach of JWST without significant gravitational lensing, there are other avenues. Pair Instability Supernova (PISN), in which a subset of massive Pop III stars end their lives, are within reach of direct detection by JWST. Regardless of whether we detect PISN with JWST, a full exploration of the parameter space of the Pop III initial mass function (IMF) is needed to determine the physics that governed Cosmic Dawn. We present results from a new semi-analytic model (SAM) which treats the slope of the Pop III IMF and the strength of the external non-ionizing UV background as free parameters. Our work will provide the basis to use the observed rate of PISN as a powerful probe of the physics which governed the formation of the first stars. In particular, we will determine constraints on the Pop III IMF for various possible observational results with JWST.