Assuming I understood your request correctly:
You want the icon to display if you have the Inquisition buff with over 5 seconds left and 3 holy power, correct?
Code:
Version:4.20; InvertAuraBelow:5; buffname:Inquisition; owntex:true; timer.enabled:true; timer.y:-100; timer.x:53
Code:
Version:4.20; thresholdinvert:true; icon:spell_holy_lightsgrace; bufftype:10; PowerType:9; threshold:3; customtex:true; texmode:2
Hope I got this right, as I don't have a paladin to test it on. Oh, and you need to enter the auraID (the number in the mouseover tooltip) of the second (holy power) aura in the conditional box (right below the buff name box) of the first (Inquisition) aura.