The Valiants are the only League Two team left in the competition, having knocked out both Sheffield clubs this season.
And Mirfin told the club's official website: "They have beaten two really good team to get to this stage and they deserve it.
"We have to respect them, and play our own game. It is a great chance for us to get through, but we have got to perform on the night.
"We're taking nothing for granted. Vale have done fantastically well to get where they are."