My chandelier is old. The grounding wire does not exist. The ceiling has a third wire. Black, white and green. Which is ground and where on the chandelier should I attach?

Attach the green ground to the spanner mounting plate that runs side to side on the ceiling box. The light attaches to the spanner and makes a ground, fixture is grounded but not the individual sockets

If this is hanging on a chain, I usually see a bare stranded copper wire laced through chain with supply wires.