how to convert the world coordination to robot coodination in PR2 ros

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I guess TF is the library you are looking for. Tutorials here. It is the ROS way to transform between different coordinate frames. For instance, if you have the pose of your object as a PoseStamped (that's a pose that also contains the coordinate frame it is relative to and a time stamp) you can use TF to transform the object's pose to the robot's base. I actually believe that the cartesian arm controller internally also uses TF to transform poses into the correct frame, i.e. passing it any valid PoseStamped should work.

If you need more complex arm motions, I suggest that you have a look at move_arm. It provides a pretty powerful interface for arm navigation. You can find tutorials here and here.