Metric Length Conversions Game
http://www.sheppardsoftware.com/mathgames/measurement/MeasurementMeters.htm
Metric Mass Games
http://www.sheppardsoftware.com/mathgames/measurement/MeasurementGrams.htm
Metric Volume Games
http://www.sheppardsoftware.com/mathgames/measurement/MeasurementLiters.htm
http://www.us-metric.org/wp-content/uploads/2015/06/Practical_Guide_to_the_SI.pdf