XYZ format is the simplest file format available in PyMOL. Minimally, it can consist of an atom symbol followed by three whitespace-delimited XYZ coordinates.
C 1.23 34.2 20.44
or
N -1.195 0.201 -0.206 C 0.230 0.318 -0.502 C 1.059 -0.390 0.542 O 0.545 -0.975 1.499 H -1.558 -0.333 0.660 H 0.482 1.337 -0.514 H 0.434 -0.159 -1.479
It is also legal to provide an atom count should you wish to do so.
3 C 0.230 0.318 -0.502 C 1.059 -0.390 0.542 O 0.545 -0.975 1.499