How do 10-year-old boys get 6-pack abs?

There is no such thing. The human body only has 3 tendinous intersections (the tendons that cross the rectus abdominis). These means that you can only have a "Possible 8-pack". However, the way to obtain a great 6-pack would be through strength training and MAINLY diet. You will need to get to a body fat low enough to see the abs. Everyone has them, they are usually just covered in fat.