And is there a time table?
To get from Orly to St Germain en Laye on Paris trains....
OrlyVal train from Orly Airport (South or West) to Antony station.
RER B train in direction Aeroport CDG from Antony to Chatelet les Halles.
RER A in direction St Germain en Laye from Chatelet till terminus station of St Germain-en-Laye.
The trains from Orly are frequent, running about every 10 minutes throughout the day.