First use the mole ratio from the balanced equation:
4NH3 + 5O2 → 4NO + 6H2O
For every 4 mol of NO, you need 5 mol of O2.
14.0 mol NO × (5 mol O2 / 4 mol NO) = 17.5 mol O2
Now use the ideal gas law.
760 mmHg = 1.00 atm
35°C = 308.15 K
Solve for volume:
V = nRT/P
V = (17.5)(0.08206)(308.15)/(1.00)
V ≈ 442 L
So about 442 L of O2 is required.