The 8th stage in Stray is called The Sewers. Thanks to our guide, you'll have an easier time reaching 100% in chapter 8 - you will find out where to unlock 2 of B-12's Memories.
Additional note - Obtaining the collectibles in the sewers will be much easier if you decide to kill the zurks you come across. If you want to earn the gold trophy first (Pacifist), then use the Chapter Select option in the main menu.
Menu location: row 3, position 2
Collectible description: You have to reach the location where Momo will partially open the gate for you before splitting up. Start exploring the infected part of the sewers pictured in the screenshot above.
Along the way, use the UV lamp to destroy the zurks and their eggs. This way, you'll safely reach the side tunnel entrance from the screenshot. Hop over there and go straight ahead.
You will reach a huge hall. Jump on the railing to unlock the memory.
Menu location: row 3, position 3
Collectible description: This collectible can be obtained shortly after you start encountering the big eyes on the walls. You have to escape the zurks and in the location from the screenshot, jump onto the lower pipe.
Go left first. Jump onto the smaller pipe and reach the tunnel entrance pictured in the screenshot.
This new passage will lead you to the location containing the memory.