In their title defence, the Indomitable Lions are set to take on the Super Eagles at the Alexandria Stadium for a ticket to the quarter-finals.
Both teams finished second in their groups to make the knockout stage.
“We have total respect for the Super Eagles. They are a good side and can improve on what they have shown so far is this competition, “Onana said at the pre-match presser on Friday.
“For us, it is a big motivation to face a good side like Nigeria. You don’t need extra motivation to play a big game.
"We expect a tough game. I expect them to play well as always. They are a very good team. But we are ready. We continue to the end.
"We're ready to play any team and we have to show that we are stronger than them."
Cameroon were denied a place at the 2018 Fifa World Cup in the qualifying rounds by Nigeria, so they will have a score to settle in Egypt.
"I was born ready, I'm preparing myself well and I am ready to play against them," Onana declared.
"I am confident and relaxed and it's what we've been training for.
"I’m excited. It’s getting exciting. Everyone wants to play such a match. We will see what happens.
"The loss to Nigeria in the World Cup qualifiers is all in the past and tomorrow's game is different."
Cameroon are unbeaten in their last nine Afcon games, their longest streak in the tournament since going 12 matches without a loss between February 2000 – February 2004.
Their last defeat (1-0) came against Cote d'Ivoire in the group stage in 2015.