There are many threads here about upgrading old versions, overall the answer is: Do it slowly, version by version, all the way through 6.x, 7.x, 8.x …, you should be able to get by with just upgrading to one patch release version for each minor version (at least that’s how it works now, I have no idea how it worked with 6.x versions)
But 6.0.2 is so old that it will take a long time (I wouldn’t bet one day of work was enough), and it might not work, in this thread:
@RodrigoPetter wrote that they had given up on going from 6.x to 11.x.