Ibeg ! the metro is tricky in france. each line has a starting point and an ending point. when you get on a metro line - you are going in either one direction or another. say you were on la ligne 8 - it goes to either balard or creteil / pointe du lac. example ↓ i will show you how to go from bastille to if you are at the bastille and want to go to pigalle: take line 8 (toward balard)- to line 4 (toward porte de clignancourt), transfer at strasbourg saint-denis- to line 2 (toward porte dauphine), transfer at barbã¨s rochechouart - arrive at pigalle. choose one of these destinations from bastille. show how you would navigate the mã©tro (just like the above example) to get to: le musée d'orsay← l'opéra

Hi !
 
Opéra > Musée d'Orsay =
When you are at Opéra métro station, take the line 8 (towards "Porte Balard")
Then transfer at "Madeleine" station  to line 12 (towards "Mairie d'Issy") and stop at "Solférino" (about 12 minutes)

Musée d'Orsay > Opéra
On the way back, from "Solférino" take the line 12 (towards "Aubervilliers/Front populaire") 

Then transfer to "Madeleine" station to line 8 (towards "Créteil/Pointe du lac") and stop at "Opéra"

from "Bastille" to "Pigalle" = 
either the way you said =
Take the line 4 (towards "Balard")
Then stop at " Strasbourg Saint-Denis"
and transfer to line 4 (towards "Porte de Clignancourt")
Then stop at "Barbes Rochechouart" station to line 2 towards "Porte Dauphine"
Arrive  at "Pigalle" station 
All together , with Bastille and Pigalle, 2 transfers and 11 stations.

OR

Take the line 5 (towards Bobigny/Pablo Picasso)
Then transfer at "Gare de l'Est" station to line 4 (towards "Porte de Clignancourt" )
Then transfer at "Barbes Rochechouart" to line 2 (towards "Porte Dauphine")
Arrive  at " Pigalle" . (about 25 minutes and if you count Bastille and Pigalle , Pigalle will be the thirteenth métro station . 

hope that's what you were asking for !!