The mass of an object expressed in kilograms is a way of expressing the amount of matter in it. The mass of an object is the same everywhere and does not depend on the acceleration due to gravity. The weight of an object on Earth is the force by which it is pulled by the Earth and is the product of the mass and the acceleration due to gravity.
As the weight of a 2.6 kg mass is 25.506 N, acceleration due to gravity in the laboratory is (25.506/2.6) m/s^2
If an object weighs 47.8 N it has a mass of 47.8*2.6/25.506 = 4.8725 kg
The mass of the object weighing 47.8 N is 4.8725 kg.