This is what i did, but could be completely wrong.
1g Cl reacts with 135x10^3g O3
1/35.5 Moles of Cl reacts with 135x10^3/48 Moles of O3
Multiply both sides by Avogradros to get number of particles of each, then divide both by the number of Cl particles = 9.98x10^3 O3 molecules
EDIT: Previously had O2, not O3