The condition for stationary wave formation is that the total distance travelled between the nodes(two) up and down or given path is integral multiple of ‘λ’
i.e ., 2πrn = nλ where, n = 1,2,3,…….
But λ = h/mv (from de-Broglie’s hypothesis)
2πrn = nh/mvn
mvnrn = n (h/2π)
i.e. integral multiple of (h/2π) should be equal to the angular momentum of electron in the orbit.