All you need to remember is that diving by x is the same as multiplying by 1/x
So every conversion can be done as a multiplication, you just define the factor appropriately.
eg meters to yards, multiply by 1.09361
When designing a class, and especially a "model" class like this, don't start with its code. Start by thinking about how you want to use this class. Jot down some examples of the method calls you would ideally like to make use of this class. That gives you the method signatures for the public methods of your class. Now start coding.
That's why I posted examples of using my converter class, rather than posting any of its internal code. Looking at the code you posted I can't see how I would use those methods to convert between two units.