How do I determine my monster's hit points?
Monsters (like explorers) don't have hit points. If a scenario says that a monster can be killed instead of just being stunned, then that scenario should also say how it can be killed. It may just say that if it's defeated, then it is killed instead of stunned, or if it's defeated with a specific item, etc. You may have to be more specific in your question about which scenario you are playing, but just double check that scenario's rules; there are no general game rules to cover this.