The frequency of the middle f note on a piano is 349.23 hz. what is the wavelength of this note in centimeters? the speed of sound in air is 343.06 m/s.

We are given that: 
Speed of sound in air = 343.06 m/s and frequency f = 349.23Hz. 
Calculating for wavelength using the formula:

Wavelength λ = c / f

wavelength λ = 343.06 / 349.23 = 0.98233 m = 98.233 cm

where is the

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m