Used to express 'when', 'if it comes to', 'in the case of'.
Long explanation:
The ~となったら grammar point is used to express a situation that 'when it comes to', 'if it becomes', or 'in the case of'. It emphasizes the idea of 'if it has come to (the point of/scenario of) X, then...'. The formation is straightforward and it can be used with a verb or noun.