United claimed a dramatic 3-1 win on Wednesday at Parc des Princes to reach the quarter-finals on away goals after a 3-3 aggregate draw.
Trailing 2-0 from the first leg and without 10 senior players due to injury and suspension, United were 2-1 up thanks to Romelu Lukaku's double before Marcus Rashford struck an injury-time penalty in the second half that was awarded following a VAR review.
After playing his part to help United become the first team in Champions League history to progress in a knockout tie after losing the first leg by two or more goals at home, Fred believes the Red Devils have the quality to reach the final in Madrid on June 1.
"Unbelievable," he said to reporters. "We had a great match. PSG are a very good team, but we always believed. We knew it was going to be difficult, but we worked hard and sought the victory until the end of the game.
"We started with lots of pressure because we lost 2-0 at home and had to seek victory and score a quick goal. Fortunately, we managed to score in two minutes and, unfortunately, we conceded a goal right after. But we showed serenity on the field to seek the victory until the end of the game.
"PSG are a great team with experienced players and young ones, too. We knew it would be difficult, but we wanted the victory. We have a team that can reach the final. We knew it would be difficult, but we wanted to win. We believed until the end and we did it."
PSG had 72 per cent of the possession but only managed four shots on target throughout the match - the same number as United.
Marquinhos feels the Ligue 1 leaders were not efficient enough with their use of the ball, but credits United for their tactical approach.
"They were a team that defended and waited for our mistakes," said the Brazil international. "We tried to play the ball to find space, we found space, we had chances to score, but we weren't effective. Efficiency was lacking.
"It's true that we missed some things about the game, but I think we managed to control the game. We tried to move forward. But the opposition wanted to defend, counter and wait for our mistakes. They played the right game."