Where do you hit someone to knock them out?

Tomorrow, I am getting into a fight with this guy cause I called him a bluff. He was picking on a Freshman calling her a , she said she would get her boyfriend to kick his ***, the guy said he wouldn't do ****. So I message her tell her he won't do anything, don't worry bout it. Well, I go to her facebook page the next day and it's blown up with hate comments and **** from him. One of my friends is arguing with him on one of the comments, I just say he's a bluff. He gets pissed and now wants to fight me. This all happened like 2 weeks ago. I am a Sopre, him a Senior. Me and him are about 5'10"-5'11" and I weigh 142 with some muscle on me cause I lift weights for football. He also plays football but since he is a Senior, has been lifting more then me, making him a bigger guy. I took Shotokan Karate for 6 years of my life, and I know some Brazilian Jiu Jitsu, and my friend's dad is an ex NAVY Seal and taught me a little Filipino Street Fighting, while his son(my friend), is a Black Belt in Tae Kwan Do and he taught me a little bit as well. Although, I only been in one fight in my life, and it was when I was like 6 and kicked a 4th grader's ***. I haven't fought since nor have practiced my Martial Arts since about 12 or 13. I am 15 now. Is there any spot that if I aim for, and hit, will knock the person out? And how hard should I hit in that area?