The converse of a conditional statement "If P, then Q" is "If Q, then P."
In your statement, "If two angles are vertical angles (P), then the angles are congruent (Q)," the converse would be: "If the angles are congruent (Q), then two angles are vertical angles (P)."
Thus, the correct answer is: "If two angles are congruent, then they are vertical angles."
(Note: While this is the converse, it is important to note that the converse may not be true in general, as there are other scenarios where angles can be congruent without being vertical angles.)