A ball is another word for skein and are packaged individually, so I think you may be misunderstanding what the 6 means. It could mean a 'size' 6 weight of yarn, like the pictures on this chart
. You need to go by the yardage the 3 'balls' in the pattern would be and find that much in another yarn, which may take 4 skeins or 2 or even one, depending on the yardage in each. What's the pattern and what yarn do you have?