Theyre not speed conversion charts really. They are speed/distance tables. One chart shows in increments of minutes I believe and the other one goes in increments of hours.
So for example: If you have a ship that is going 7kts and you want to see how many kilometers it will travel in, say 10 hours, you just go down the left hand column till you find 7 and trace that across to the right till your under the column that says 10. There you have it, the distance in kilometers that a ship will travel in 10 hours at 7 knots.
As for you crashing problem:hmm: You say it happened after starting with SH3 commander? Try and start the game normally and see if you still have the problem. If not then you will know there is a conflict going on with SH3 commander. Again, what order did you install your mods in?