Just follow the given steps for do this.
1. If your facebook profile is not connected with yahoo mail then you first create an email id in yahoo and connect your facebook account with yahoo email id.
2. Now You login To Yahoo Mail And Then Go To The Contacts Tab.
3. Now You click on Import Contacts
4. Now Click On Facebook
5. In Pop up You Will Get Message That Do You Want To Share Your contacts with yahoo. and now click on ok !
6. Now You will Get A Message .
Now You are done :) Click on View Imported Contacts And See You Facebook Friends Email ids .