There is no right episode. The movies does not follow the story line.
Well, it was released between 50 and 6, but anytime is okay. Whenever you like. I love the movie sooooo much!!! well as me there is no time for that its not after an episode
The first minutes of the first Shippuden episode is the same as in Shippuden episode 51.
I am not sure because I don't know when the last episode of Naruto Shippuden is.
Naruto Shippuden - Episode 166 - Confessions Naruto Shippuden - Manga 437 - Confessions
he doesnt come back til shippuden like 280
The last Naruto Shippuden episode is episode 64
Naruto shippuden episode 221
Naruto Shippuden episode 3
Naruto Shippuden Episode #26
It starts in episode 19 (shippuden)
Naruto Shippuden episode 29-30
It starts in Shippuden episode 2 but all the attacking starts in episode 3. Episode 2 was just showing them getting ready for the fight at the end.