HOW DO I GET A SERIAL NUMBER FOR World of ea games collection bought at half price books?

The Serial Numbers for the games in World of EA Games are located on the back of the instruction booklet that it comes with.

If you bought it used, or if the instruction booklet is simply missing, you should try to exchange it, return it, or contact EA themselves; they may be willing to give you a refund or allow you to exchange the game directly with them.