Third Grade Math Worksheets For Kids - Free & Printable ... 3rd Grade X Math X. Metric System: Units Of Weight. Units of Volume: Convert Cups, Pins, Quarts & Gallons. Units For The Measurement Of Capacity - Cups, Pins, Quarts & Gallons. Metric Units Of Weight: Grams And Kilograms. Units Of Weight: Ounces And Pounds. Learn Metric Units Of Length. Convert The Unit Between Meters, Centimeters and Millimeters.