To get past the first set of turrets to find Classi in The Thin White Line in South Park: The Fractured But Whole use time controls to stop time and walk past the turret and turn the first turret off. Use Snap N Pops to break the box and enter the vent:
Go to the top exit and use Snap N Pops to pop open the wire box:
Enter investigation mode and hover over the wire box and select the hamster icon. Go to the highlighted area and follow the button prompts.