When Trump said last night (transcript here) "Well I like the mandate" he didn't mean the individual mandate in Obamacare. Trump may not even have been aware that that's what Anderson Cooper was talking about.
Instead, Trump has his own idea in his head which means that there ought to be a mandate which applies to the government, not to the individual, which states that it is government's responsibility to provide healthcare to people who can't afford it and would die without it:
"I don't want people dying on the streets and I say this all the time."
"The Republican people, they're wonderful people. They don't want people dying on the streets."
"[T]here's going to a group of people at the bottom - people that haven't done well. People that don't have any money that won't be able to be care of [sic]. We're going to take care of them through maybe concepts of Medicare."
"You cannot let people die on the street, OK?"
"That's called heart. We gotta take care of people that can't take care of themselves."
That's all that's going on there, folks, despite what Ted Cruz partisan Rush Limbaugh is telling you in the show opener today. The mandate's in the "we're going to" and the "cannot" and the "gotta" in those statements.