There's more to waves than just the wavelengths. Microwaves are a form of electromagnetic waves, which means they're oscillations of electric and magnetic fields. Sound waves, on the other hand, are compressions and decompressions of air. Our ears are sensitive to the latter, but not to the former. (With our eyes we can detect electromagnetic waves, but only over a limited range, and microwaves fall outside of this.)
While this is true in general, there actually exists a somewhat ill-understood microwave auditory effect where people perceived sounds due to electromagnetic radiation at microwave/radio frequencies. The cause is thought to lie in the radiation heating parts of the inner ear, leading to a perception of sound. You will not observe this with your kitchen microwave, though, since that was designed to not have any radiation escape.