How do you know what your dream is and if you dont know how can you find one?

As boring as this may sound research is the best answer. Check things out in all areas to see what actually catches your interest. For some it may be science or mathematics. Maybe literature or cooking. You really just need to dive in to things to find the things that interest you the most and be prepared to be surprised. Something that may not seem like something you'd like may actually be just the ticket.