3. What is the volume of an object that is 12 cm long, 100 mm high, and 000.1 m high

First, you have to convert the numbers into one single unit. You could do mm or m but I'm converting the numbers into cm

12 cm = 12 cm

100mm = 100/10 = 10 cm

000.1 m = 000.1 x 10 = 10 cm

Now that the numbers are in one single unit, you can now just use the volume formula

V = (L) (W) (H)

V = (12cm) (10cm) (10cm)

V=1200 cm ^3