The Scot struck twice in the 2-1 win.
"It was a massive win for us," Adam said. "Especially against a team like United, with the quality they have.
"But at home we fancy ourselves against anybody, it is away from home we have to pick it up.
"Today I thought we were excellent even though the conditions weren't great.
"The first goal was a bit lucky, but we will take that and it is a massive three points for us."