Iraq advanced to the intercontinental playoffs when a 2-1 win in Basra on Tuesday completed a 3-2 aggregate victory over the United Arab Emirates in the fifth round of Asia's preliminaries for the expanded 48-team World Cup.
Bolivia, who finished seventh in South American qualifying, will take on Suriname, with the winners to meet Arnold's side in Mexico, with the dates and venues for the games yet to be announced.
"We have to stay positive and make sure we get prepared for this game," said Arnold, who replaced Jesus Casas as head coach in June.
"It's in Mexico, somewhere we haven't played before, so the off-field preparation will be crucial."
Iraq made their only appearance at the World Cup in Mexico in 1986.
Arnold is no stranger to guiding teams through high-pressure playoffs, having steered his native Australia to the 2022 finals via wins over the UAE and Peru.