If you are 15, then the answer toyour question is a pretty straightforward, 'no'
There's the law of conservation of mass. In any closed process, mass will be conserved. That is to say, what ever you do to something, like heating, or streching or even chemical reactions, the mass of the original will remain the same (In a chemical reaction, the total mass will remain the same).
For older students,the law of conservation of energy takes precedence, because mass and energy can be interchanged (Einstein's famous E=Mc^2).
So it kind of depends on how the question is framed. Most scientists would interpret your question as , "Is it possible to apply some process to an object such that all its fundamental properties start at one value and after the process take different values" The answer to that is no.
You might be able to change length or density, but not mass (or, if we are in a relativistic frame of reference, energy).
If you mean "Is it possible to switch fundamental units from, for example metres, seconds, kilograms into feet, seconds and pounds" Then the answer is yes. Some of the derived units might be pretty complex and the sums wold be harder, but it's eminently do-able.
Good for you for thinking about this stuff. Keep it up! :)