Hello, Alyssa,
The term "mole ratio" refers to the porportions as documented in the balanced equation of these two substances. For this reaction:
2CO+O2 -> 2CO2
the mole ratio of CO to CO2 is 2CO/2CO2 or 1/1 or 1. We'll get 1 mole of CO2 for every 1 mole of CO.
Bob