from Yahoo Chat, How can i know that Exactly from where my friend is talking to me?
The problem is that you are connecting throught Yahoo Chat. To get the IP number you need to exchange emails. Then you can get an IP number from the email header. But, he might spoof the header with common techniques or use a proxy server.
Remember, that anything you can check on him, he can check on you.
Do some social engineering. Since you are chatting ask for an email exhange, or ask for his name and city. Then you can discover his IP number location, or with his name you can run an online background check to discover a lot of things like his current address, address history, criminal record, civil liens and judgements against him, etc.