Need a pendulum has 702 j of potential energy at the highest point of its swing. how much kinetic energy will it have at the bottom of its swing?

It depends.
1. If its a complete question, assumption : The PE at the bott of its swing is zero.
It will have 702J of KE at the bottom of its swing because all of the PE will be used to speed up the pendulam bob.
.
If the PE at the bottom of the swing is not zero , say its PE'.
then spent pot. energy will be initial PE - PE'
and hence this will be the amount of KE at that point too.

Can you give more detail