How to calculate the kpa of the given plate on earth's pressure where: length is 3500mm, height is 2300mm, thickness is 75 mm.
You seem to want to calculate the pressure exerted by the plate on the earth's surface (specific and the dimensions should have been stated clearly in the drawing).
Pressure exerted = Force/Area
In this case Force is equal to the weight of the plate.
Weight of plate = mass*g ( acceleration due to gravity)
Dimensions of plate are length = 3500 mm = 3.5m
Width = 2300 mm = 2.3 m
Thickness = 75 mm = 0.075 m
Assuming the material of construction of plate to be steel ( it has not been stated in the question) , density of steel(assumed) = 7750 Kg/m^3
Volume of plate = 3.5*2.3*0.075 m^3 = 0.60375 m^3
Therefore Weight of one plate = 7750*0.60375*9.8 =45854.8125
Force exerted by plate on the earth = Weight/Area
= 5696.25 Pascal
= 5.7 KPa
Assumptions : Material of construction of plate as steel with density(7750 Kg/m^3) , single plate lying flat on the earth surface.