How much hydrochloric do I add to 150 mL of water to adjust pH by 1 level?

The amount of acid/base needed to adjust pH by 1 level depends of the initial pH of the water/solution.

Suppose the pH of the water is 7, and the change of volume of water/solution is negligible on addition of HCl or NaOH.

Initial [H⁺] = 1 × 10⁻⁷ M

When HCl is added, it changes from pH7 to pH6.

Final [H⁺] = 1 × 10⁻⁶ M

Increase in [H⁺] = [(1 × 10⁻⁶) - (1 × 10⁻⁷)] = 9 × 10⁻⁷ M

Moles of H⁺ needed = (9 × 10⁻⁷ mol/L) × (150/1000 L) = 1.35 × 10⁻⁷ mol

Moles of HCl needed = 1.35 × 10⁻⁷ mol

When NaOH is added, it changes from pH7 to pH8.

Final pOH = 14 - 8 = 6

Final [OH⁻] = 1 × 10⁻⁶ M

Increase in [OH⁻] = [(1 × 10⁻⁶) - (1 × 10⁻⁷)] = 9 × 10⁻⁷ M

Moles of OH⁻ needed = (9 × 10⁻⁷ mol/L) × (150/1000 L) = 1.35 × 10⁻⁷ mol

Moles of NaOH needed = 1.35 × 10⁻⁷ mol

you are looking for an easy answer that doesn't exist

You add as much as need to reach the desired effect. I really don't like to help people cheat on their coursework.