Density is mass per unit volume. A cube with dimensions 0.82 cm by 0.95 cm by 2.548 mm has a volume of
(0.82 cm) × (0.95 cm) × (0.2548 cm) ≈ 0.1985 cm³
Then the density of this cube, given that it has a mass of 0.572 g, is approximately
(0.572 g) / (0.1985 cm³) ≈ 2.88 g/cm³