Both teams go into tomorrow's Old Trafford clash with back-to-back Premier League victories.
Wolves held their own against Manchester City last month, drawing 1-1 at Molineux, and Nuno said: "There is no game I recall that we changed.
"That tells a lot about what the players believe. If you change, it doesn't make sense.
"You have to adapt, respect and be humble – know you are facing a strong team – but you cannot change and fear.
"None of those things are part of us. We go there to compete, believing in ourselves."
It is the first competitive meeting between Nuno and Jose Mourinho as managers.
The pair know each other well though as former goalkeeper Nuno was part of the Porto squad that Mourinho led to Champions League glory in 2004.
Mourinho has praised Nuno for how Wolves dominated the Championship last season.
In return, the Molineux chief said: "For me, it's an honour that Mourinho speaks about me.
"He's a fantastic manager. But it's not about me, the game is about Wolves.
"Tomorrow, it is two good teams trying to achieve the best result possible."
Wolves have not won at United for 38 years.
"That says how hard it is to go to Old Trafford," added Nuno.
"The last results of Manchester United shows the quality they have – two victories in the Premier League and then in the Champions League.
"It's a good team – fantastic players, fantastic manager. We go there to compete, like we always do."
"I expect tomorrow we enjoy (it) together, to compete against one of the best clubs in the world."
Nuno has no fresh injury worries for the game.