C-SPAN has the relevant video.

From ABC News summary:

Trump tried to explain his own remarks recently in which he appeared to accept he lost the 2020 election, including his comment last week that he “lost by a whisker.”

“I said that?” Trump said on the debate stage when it was read back to him.

“Are you now acknowledging that you lost in 2020?” ABC News moderator David Muir asked.

“No, I don’t acknowledge that at all,” he said. “That was said sarcastically.”

Asked about the peaceful transfer of power, Trump did not say that he regrets anything about his actions on Jan. 6, 2021. He claimed he had “nothing” to do with what happened that day, which culminated in an attack on the U.S. Capitol.