On this page of guide Dragon Ball Z Kakarot, you will discover the complete progress of theFriends Forever sub story.
Episode: Cell Saga - Episode 8
Period: From "Evanescent Normality - episode 8" to "Son Gohan goes wild - episode 9"
Go see Franky in the North Mountains area (pictures1and2).
1 picture
2 picture
After the scene, return to the northern mountains area and collect all the documents (pictures3and4). Finally beat the robots to close this sub story (picture5).
3 picture
4 picture
5 picture