The Spaniard scored the first and forced an own-goal for the third as the Blues ran out comfortable 3-1 winners over Mexican side Monterrey to seal their spot in the final.
Mata admits that Rafael Benitez's men are taking the competition seriously and was happy with the way they applied themselves against Monterrey.
He told BBC Sport: "I am so glad today for winning, the way that we won, for us it’s a very important tournament we want to win this trophy, to be world champions on Sunday and we will do our best to win.
"I am very happy with the goal and the result, I think we started really well, we were really focused on scoring more goals and we did. 3-1 is a good result for us."
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Corinthians secured their spot with a 1-0 win over Al-Ahly but created several chances and could have won by a greater margin.
The 24-year-old is wary of the threat the Brazilian's pose, but is confident Chelsea will make the trip to Japan worthwhile but bringing home the trophy.
He added: "We have confidence about winning but we know Corinthians are one of the best teams in South America. It will be a football party and hopefully we will win."