The converse of the implication a ⇒ b is b ⇒ a. That is, the converse of
"If a, then b"
has the predicate and conclusion swapped, as in
"If b, then a"
So the converse of
"If a number is divisible by six, then it is divisible by three."
would be
"If a number is divisible by three, then it is divisible by six."
(Of course, this statement is not true; consider the number 3, which is not divisible by 6.)
