Try importing the IDF into the corresponding version of OpenStudio, which will retain most EnergyPlus objects except for HVAC (see this question for more details). Then:

1. Save the OSM file

2. Check all the Ideal Air Loads boxes on the Thermal Zones tab (or add Add the Enable Ideal Air Loads For All Zones measure (or check all the boxes on the Measures tab) Thermal Zones tab)

3. Run the OSM to generate the out.idf from OS, which can be found in the <osm folder>/run/#-EnergyPlusPreProcess-0