suppose you were able to blow air out of your mouth at one third of an atmosphere pressure. How tall a column of water could your mouth air pressure push up a straw?

I know atm pressure is 1 atm
but I'm really confused about how to go about this problem. thanks!

the equation that I think I need

is P = P0 + ρgh
where P is 1 atm and P0 is 1/3 atm
but I get a height of 3.06 x10^-4 meters
which seems like a vvery small amount