We don't know what was in those documents Trump took. We do know they weren't his to take
The FBI has given us a rough inventory of how many top secret, secret, and confidential documents it found at Mar-a-Lago, former President Donald Trump’s country club home in Florida. But we don’t know what was in these classified documents, why they were classified, whether they had ever been declassified, and whether there was any potential harm to the United States or our allies by these documents being held haphazardly.
Source: washingtonexaminer.com