The League Two side have already knocked out Tottenham and Crystal Palace from this season's competition.
Ahead of tonight's tie, Pell declared: "The Cup has been the highlight of our season so far. I think we have earned the right to be in the quarters, and earned the right to have a cup tie away at Old Trafford.
“We are not going along just to make up the numbers - the boys will be wanting to do a job on them. The pressure is definitely on Manchester United, not on us.
“That pressure will soon ramp up if they are being held by a League Two team in front of such a big crowd.
“It's definitely a highlight of anyone's season. Our fans will play their part. They have a team they can be proud of, to get this far in the cup.
“And who knows when that will stop?"