Hi there,
If you're looking for a basic metric conversion chart, here's one you can use:
http://www.sciencemadesimple.com/metric_conversion_chart.html
You may also want to try a rhyme or acronym, to help him or her remember basic metric units of measurement: Kilo Hecto Deca Unit Deci Centi Milli (KHDUDCM). From there, you can either make up an acronym, with a word starting with each letter of the units of measure, or use one that's tried-and-true-- like "King Henry Doesn't Usually Drink Chocolate Milk."
It may also help to compare the metric units of measurement to everyday objects, to make the concept more real. Here are some ideas for how to do this:
http://www.education.com/reference/article/referents-common-metric-measurement/
Lastly, the final link: a "Make Your Own Ruler" activity, might be helpful, too. You could try this activity using metric measurements. Perhaps, going through the process of building a ruler of his own will bring the concept of increments of metric measurements home for him.
Hope this helps!