After losing the first leg 1-0 at Estadio Do Dragao, the Serie A outfit will look to overturn the deficit at Stadio San Paolo in the return clash.
Benitez is aiming to win Europe's second-tier competition for the second successive year after guiding Chelsea to the 2013 Europa League with a 2-1 triumph over Benfica.
Napoli head into the contest on the back of a morale-boosting 1-0 success at Torino on Monday, which came courtesy of a last-gasp winner from Gonzalo Higuain.
And Benitez says his side are in a buoyant mood ahead of the encounter.
"We reach this game (against Porto) with confidence, because we won a difficult test (against Torino)," he told Sky Sport Italia.
"We need to get everyone fit again and hope we are fresh for a match that will be like a final."
The Spaniard also praised the performance of midfielder Marek Hamsik, who has enjoyed a difficult period in Italy's top flight this term but put in an assured performance against Torino.
He added: "He did much better, as he helped out the team in attack and defence. I never thought of bringing him into a deeper role, as he is so good at the final ball and those runs forward.
"I said that I had faith in him and he replied with a good performance. I think he needs to have freedom to do what he wants on the field."
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