I have a room with two sets of lights. One set is controlled by a
single pole switch. The other set is on a three way switch. How do I
combine them so that all the lights are controlled by the 3-way
switches?

Conveniently, the single pole and one of the three way switches are
double-ganged in the same switch box.

Also I have power from different circuits running to each of switch
boxes (one is for the single, the other is for the three-way).