Quote:

Nothing ever ceases to exist(die) it just transforms(evolves or deliberate changes turns it) into something else.



you fill a nuclear reactor with 100 kg Uranium
After the reaction you have 99 kg mass
The reactor delivers to the ambient the amount of energy
E = 1 kg x c^2

Following your assumption something having 1 kg mass has been turned into energy
But what ?
The total number of proton,neutrons and electrons inside the reactor is still the same
Not even one material particle get lost