The nearest lines (20 meters) are 42, 88 and 70. If a 5-minute walk you can take the bus 62 which will take you directly to the Parc des Expositions Porte de Versailles.
See the : Paris bus plan
To arrive / come from Roissy CDG airport, you can take the Bus Direct. The closest stop is “Tour Eiffel / Suffren” (easy to reach thanks to buses 42 or 30). Le Bus Direct CDG
To arrive / come from Orly airport, you can take the Bus Direct. The closest stop is “Trocadéro” (easy to reach thanks to the metro, line 6). Le Bus Direct Orly