While coming from CDG airport (Charles De Gaulle)

The fastest solution (1 hour) and less expensive: To take train the RER B (Paris direction) and stop  at "Chatelet les Halles" , then to go during 300 meters to "Bourg L'Abbé" street or: make a transfer to line 4 (Direction of Clignancourt) and get off to the following station " Etienne Marcel" then walk 100 meters.

Solution

In the event of strike of the RER: To take Roissy bus of the RATP or the Air France Bus, Paris direction.

Last solution: The taxi via A1 motorway (to avoid the rush hours)

Coming from  ORLY airport take the automatic train Orlyval (to Antony station), or the Orly Bus Paris direction (go down in Denfert-Rochereau) then to take line 4 direction clignancourt get off  at "Etienne Marcel " (Direction Clignancourt) then walk 100 meters.

Coming from the North Station (Gare de Nord)To take line 4, direction "Porte d'Orleans" , get off at "Réaumur-Sebastopol" , then walk 100 meters untill "Bourg L'Abbé" street.