Steve Bruce's men will be the favourites for Sunday's meeting with the League One side at Wembley, having enjoyed a fine season on their return to the top flight.
Hull currently sit 12th, nine points clear of the relegation zone, and appear all but assured of Premier League survival.
Elmohamady is glad he and his team-mates can take on United without any worries, but insists Nigel Clough's side will not be taken lightly.
"We can look forward to the cup game and what is going to be a big game for us as players, for the fans and for everybody in Hull," he told Hull's official website.
"We have a week to build up to it and to focus on what will be a difficult game against Sheffield United. They are a good team.
"We're all concentrating on that game now and trying to make everybody happy by making it to the final.
"We don't want just one trip to Wembley this year. To go twice in a few weeks would be fantastic."
Arsenal and Wigan Athletic meet in the first FA Cup semi-final on Saturday.
