Benitez’s side booked a place in the competition’s fourth round with a 3-1 win over Luton Town on Saturday.
Ayoze Perez scored twice – and Jonjo Shelvey also found the net – in front of a 47,069 crowd at St James’s Park.
Benitez named a strong starting XI for the game.
Man in life-threatening condition after 'serious collision' involving car and pedestrian in South Shields
Campaigners rally against Local Plan after farmland in Cleadon earmarked for 156 homes
Appeal to find owner of lost Labrador after dog found near Jarrow Cemetery
Pair set up cannabis farm in town centre flat
South Shields man jailed for terrifying physical and sexual assault on woman in her own home
Only goalkeeper Freddie Woodman – handed his debut – had not been a regular for the club in the Premier League this season.
“A lot of times you see managers pick lesser teams in the cups, but our manager named a strong one,” said captain Lascelles. “He said to me before the game that we want to go out there and win and see how far we can get.
“It’s not like the Championship when you are playing Saturday-Tuesday-Saturday.
“You usually only play once a week in the Premier League, so it’s not as if you need to rest players. The players are happy with that – we want to play.
“He didn’t have to rest anyone because we don’t have another game for a week.”
The cup victory followed the club’s New Year’s Day win over Stoke City at the bet365 Stadium.
And Newcastle have some welcome momentum ahead of Saturday’s Premier League game against Swansea City at St James’s Park.
Lascelles said: “Every game we play we want to win.
“I thought the boys conducted themselves really well.
“We’re in a position where we do need to focus on the Premier League, but we knew we had a good chance (against Luton).
“We want to see how far we can get in the cup without taking our eye off the league for one minute.
“Obviously, you fancy your chances more in the cup the longer you’re in it.
“Your preparation has got to be the same whether it’s your first game in the cup or the final.
“You’ve got to have the same focus for every game.”
Newcastle hadn’t won at home since October 21.
Lascelles said: “Ayoze has scored two goals, and that gives him more belief. Jonjo was due a goal as well.
“Different people are scoring for us, and it’s important that it’s not just one or two.
“The whole team’s starting to get goals now. It’s definitely a confidence booster, and now we’re really looking forward to Saturday.”
Lascelles says every United player wants to play in the cup games.
The 24-year-old added: “Everybody wants to play and is pleased to be picked – that wasn’t always the case.
“In the past, some players may have looked to have this weekend off after the busy period. It certainly wouldn’t happen now.
“We have a good group of lads here and everyone wants the same thing.”
The last Newcastle captain to lift a major trophy was Bob Moncur in 1969.
Lascelles said: “Yes, it’s something I would love to do. That would be a dream come true for me. I lifted the Championship trophy last season, and would love to lift the cup.
“But it’ll be tough. A lot of teams want to win it and will fancy their chances. But you never know.”
Lascelles was forced off against Luton after feeling his groin in the first half.
“I’m fine,” he said. “I felt it go a little bit and took no chances. It’s nothing, really, and I’ll be training Tuesday. I felt it a bit and didn’t want to make it worse.
“I think I made the right decision to come off and get it right for Swansea.”