The Spain international also lamented the temporary loss of head coach Tito Vilanova, and compared his absence to that of an "orchestra without a conductor"
The Blaugrana were defeated 2-0 at San Siro in February and will need to pull off an historic comeback in the second leg to have any chance of progressing beyond the last 16.
"AC Milan are a competitive team with a great history, and we knew it would be a difficult clash," Pique told Sport.
“We will attack all game long and be faithful to our style, so we hope to win 3-0 at home."
Barca remain without head coach Tito Vilanova, who is in New York receiving treatment as he recovers from a cancer relapse, and Pique insists that the team must progress without him in the short-term.
"Tito is greatly missed," the Spain centre-back added, "We trust him and want him back.
"We are in a difficult situation without a coach; we are like an orchestra without a conductor. But we'll get over it; Tito is helping us from New York.
"The most important thing is his health and we do not want to put any pressure [on his return], so we will wait until he recovers."
Jordi Roura has been in temporary charge in the absence of Vilanova, and he guided the Catalans to a 2-0 victory on Saturday night.