I think there's a few digits missing here even. 1 mol = 6.022E23 particles = 22.4 L at STP for an ideal gas, and 1 m^3 = 1000 L

Of course real air isn't quite an ideal gas, but some reasonable approximations [1] come out to 2.53E25 molecules (N2 and O2) per cubic meter at 15 C and 1 atm.

[1] https://www.quora.com/How-many-air-molecules-are-present-in-...