All factory joints (ball joints, ujoints, cv's) are sealed and do not have zerks. Your truck being a 2000 I would not be surprised if some parts have been replaced with aftermarkets which have the fittings. The best answer is simply to grab a good light and go looking. There is no way to add a zerk to an existing sealed joint, though sealed ball joints and cv's can be greased with a needle attachment.
The real question is are you asking because things are squeaking/creaking/groaning. If so they are very likely already shot and in need of replacement. Adding lube may quiet the noise but wont reverse any damage to the joints. There are very good instructions with pictures in the sticky section on how to replace them.