# 3-dimensional particle in a box

If I know how to get a wave function for a 3-dimensional particle in a box problem, what adjustments must I make to solve the same problem for a particle traveling in the +z direction in a tube of infinite length?

Box:
0<x<a
0<y<b
0<z<c

Tube:
0<x<a
0<y<a
0<z<infinity