Pretty much any scientific calculator will have two logarithm buttons, (though they could be on a single button with one of them accessed via a shift key of some sort).
The ln option is for calculating the natural log of the number, that is, the log base e.
The other option, log, is for calculating the log base 10, which is the one that you are after.
So, enter a value for x, calculate its log, and multiply that by 3. That will be the corresponding value for y.
The data that you give is correct, as you may verify. You might though want to fill in some intermediate values !