How often should i perform HIIT

[buffdaddy110]

I currently do a full body workout 3 days a week and cardio 3 days a week. I just started doing HIIT last week, but I still want to do some steady state cardio (running 2 to 3 miles). I was wondering if I should run twice a week and HIIT once, or run long distance once and HIIT twice. I'm in the military and need to be able to run 1.5 miles for time annually, that's why I need to do some long distance. I'm also trying to cut a little mid section fat (arent alot of us). Any suggestions would be greatly appreciated.