If there was a tape of Trump saying it, they would have linked the tape. They didn't. So I would bet a very expensive steak dinner that no such tape exists. And even if he did say it, it would have been mocking the people who might object to a black person winning.
Omarosa, a contestant on Trump's reality show "The Apprentence, also claimed to that Trump used the N word. The two of them hit it off and he hired her for a slot in his administration. (She had also worked in the Clinton administration.)
Omarosa offended pretty much everybody in the Trump White House and West Wing. I think it was Politico that reported she was fired for unauthorized use of government vehicles, mishandling of cash and other ethics violations. She spent most of the next year, including her time on the TV reality show "Big Brother" with backhanded insults of President Trump, and she had scathing remarks for Mike Pence who she really didn't like. She published a book that emphasized all that and released tapes she had recorded secretly in the White House that was seen as one of the most egregious security violations in history though the content didn't rise to the level of violation of the Espionage Act. In 2020 I think it was, she was forced to repay the U.S. Treasury over $60,000.
I bet you wouldn't have to scratch much below the surface to find the deep state operatives digging up these people and perhaps paying them to smear Trump.