The first law of thermodynamics states that (triangle) E = Q-W. is this also a statement of the principle of conservation energy

Yes, the first law of thermodynamics was created using the law of conservation of energy that is applied in a thermodynamic systems. the first law of thermodynamics is the change in internal energy of an isolated system is equal to the amount of heat (Q) added to the system minus the work (w) done by the system to the surroundings. while the law of conservation of energy states that in an isolated system that energy is constant, and energy can change its form but it cannot be created or destroyed.