The striker was one of several impressive performers in the win over Norwich.
The Magpies were without a win this season after Steve McClaren took charge at St James' Park in the summer, with speculation increasing that the former Derby County manager was about to lose his job.
They secured their first win of the season against Norwich on Sunday in spectacular fashion though as they run out 6-2 winners, and Mitrovic insists they were confident despite their poor start.
"Finally, we showed we know how to play good football for 90 minutes. We played like a real team,” he told nufc.co.uk.
"I always believed we had more quality than we had shown so far this season. We always had confidence - we never lost it, even when we were losing games. We always believed in ourselves because we know we are a good team and that we can make something special.”
The headlines will be firmly upon midfielder Georginio Wijnaldum following the game as he bagged four of his side’s six goals in the game.
While the game is one the Dutchman is unlikely to forget in a hurry, it was also a special one for Mitrovic as he bagged his first goal for the Magpies.
The Serbian has already become a fan favourite at the club and was treated to a standing ovation as he was subbed off late on, and he says it was an amazing feeling to finally break his duck for McClaren’s side.
"It is always an amazing feeling to score a goal but even more so here at St. James' Park," added Mitrovic.
"It has taken me a few games to do it but I am happy and proud to score and hear the noise from the crowd, celebrating my goal. I want to thank my teammates because they have helped me a lot since I came to the club and they help me score goals.”