If you install new brake pads on old rotors that don’t have the proper finish the brakes can make noise. And if the brake rotor finish is really messed up the noise will probably get worse and the brake pads will wear out quicker.
If this isn’t an everyday vehicle you’ll be good for now. But eventually the rotors will warp from poor friction material contact. When this happens replace both the brake pads and rotors.
Tester