Capture all the bijuus.
really cause i thought it was to put an end to all wars.
Nagato has mentioned a three-step process to work their way towards this goal.[8] First, they plan to obtain a large amount of money to support their organisation.[8] Second, they plan to set up a mercenary group loyal only to Akatsuki.[9] To build their reputation, they plan to accept any mission below the usual cost and operate off of the excess funds earned in the first part of their plan.[9] Because there haven't been any wars in some time, many of the more powerful and well known shinobi villages couldn't afford to accomplish such missions as such low prices, leading the smaller countries to hire Akatsuki over the more expensive shinobi villages.[9] By using the tailed beasts, Akatsuki would start wars and then immediately quell them, solidifying their reputation and convincing every country to depend on them, thus cornering the market in shinobi labour.[10] Without any business, the other shinobi villages would collapse due to the lack of funds.[10] Finally, after Akatsuki is the only major force of shinobi in existence, they can easily conquer the other countries.
Nagato's own interpretation of this plan not see Akatsuki conquering the other nations, but rather using the power of the tailed beast as a means to frighten the world into no longer fighting. By using a powerful kinjutsu, Akatsuki could crush one side of the war and scare the other into not fighting for a time, until the inevidablity of humans fighting causes war to continue, where the kinjutsu would be used again. Thus the cycle would repeat, creating small periods of peace in an endless chain of hatred.
After becoming Madara's sucessor, Obito Uchiha manipulated Nagato into becoming his pawn in the collection of the nine tailed beasts. As per Madara's plan, instead of using the power of the tailed beast to start and end wars, he would use them and the Demonic Statue of the Outer Path to recreate the Ten-Tails become its jinchūriki. Doing this he would be able to cast the Infinite Tsukuyomi off the moon, trapping the entire world under his genjutsu and granting him the power to create the world he wanted. Of the original Akatsuki members, only Kisame Hoshigaki and Zetsu were aware of this true plan.