Benitez's men are third in Serie A and host League Cup holders Swansea at the Stadio San Paolo with all to play for, having been held to a goalless draw in the first leg in Wales last week.
"We want to progress and in order to do that, we need to score more goals than they do and win," Benitez said. "This is a crucial game for us.
"We are confident because we can do good things this season."
Benitez is aware his players will have to play better than they did in the first leg at the Liberty Stadium.
"We already saw that Swansea play great football," he said. "We have to play as we know how, but we must increase the tempo."
Napoli are considered firm favourites to progress but Benitez refuses to take the Swans lightly.
"I know Swansea well," he said. "They did a great job against us as well as against Liverpool at the weekend.
"They scored three goals against the Reds, but they also conceded four. They have a team capable of progressing to the next round of the Europa League.
"We have to be ready, we need to be clinical in attack and strong in defence. We need to impose our game."