The prophecy of St. Malachy is a document that purports to be a description of future popes.
Most scholars consider it a forgery. It is marvelously accurate up to a certain point and time and then gets vague. There is no evidence for its existence for several hundred years after it was allegedly written.
I wouldn't put a lot of stock in it. See:
Catholic Answers also has a segment on the prophecies of St. Malachy near the end of their web page on Prophecy.