He said: "Old Trafford is not like Anfield, that has an incredible atmosphere. It will be a crucial game for them after playing at Chelsea, especially knowing they won't find it easy to play against us."
United boss Sir Alex Ferguson has blasted the club's supporters in the past for not making enough noise on European nights.
Henry also taunted Fergie by reminding him of United's quarter-final loss to Monaco 10 years ago.
The French striker said: "I remember we drew 0-0 at home and people were saying we were out.
"But we showed you can score a goal at old Trafford and we finished 1-1 and we went through. Monaco are not one of Europe's big clubs and to go to the semi-final and also score at Old Trafford was incredible.
"They were a different team but still Manchester United - they won the League that season.
"This time I am confident we will go through if we play at our level.
"It's true that in the second leg at Old Trafford we will see a different United. We will have more open spaces to exploit but they can also pose a threat."