You can listen to the recording on the article.
From the text:
The recording, which first aired on CNN’s “Anderson Cooper 360,” includes new details from the conversation that is a critical piece of evidence in special counsel Jack Smith’s indictment of Trump over the mishandling of classified information, including a moment when Trump seems to indicate he was holding a secret Pentagon document with plans to attack Iran.
You only have to believe your own ears. It’s a tape with corroborating witnesses who were in the room.