Would've been better if you quoted him correctly. Below is what I found in an AP Fact Check from today, which is not quite what you said he said. Did he say what you said somewhere else?
Now you know I only hear what Trump says from you.
TRUMP: “I’m not sure that I’ve ever even heard of a category 5. I knew it existed and I’ve seen some category 4′s. You don’t even see them that much. But a category 5 is something that I don’t know that I’ve ever even heard the term other than I know it’s there.” — remarks Sunday at FEMA headquarters.
THE FACTS: In his third hurricane season as president, Trump has had plenty of exposure to category 5 storms.
He made the same claim two years ago, saying he wasn’t aware of category 5 storms until Hurricane Irma. “In Florida, you got hit with the strongest winds ever recorded. It actually hit the Keys with a_it was a Category 5. I never even knew a Category 5 existed,” Trump said in September 2017.
Since then, he’s repeatedly marveled about the size of the storms — and by extension, his administration’s response to it — including category 5 hurricanes Irma and Maria in 2017, Michael in 2018 and now Dorian.
Link: https://www.apnews.com/216c399b112c48008846071cff823be5