Studs x10 is a Red Brick in LEGO City Undercover which multiplies the value of collected studs by ten. This stacks with other stud multiplier bricks for a maximum multiplier of 3840.
During Special Assignment - Fly Me to the Moon, after reaching the top of the elevator, use Rex Fury to open an orange-handled box near a dome. Opening the box reveals LEGO parts. Assemble them to reveal a red light. Shoot the red light with the Color Gun to gain access to the dome and collect the red brick.