how to convert 40 inches X 48 inches X 5 feet high with 520 pounds to cubic meter?

1 inch is 0.0254 meters, so you rework the sides:

1.01600 meters x 1.2192 meters x 1.52400 meters

multiplying those three numbers together you get 1.8878 m^3

you can disregard the weight measurement, it is not needed

The 520 pounds part is irrelevant, unimportant. We’re talking about VOLUME, not WEIGHT.

First, convert all the measurements to feet.
To do this, we divide the inches measurement by 12:
40 inches / 12 inches per foot = 3.333333feet
48inches/ 12inches per foot = 4feet

So, our dimensions are:
3.333333feet X 4 feet X 5 feet
=66.66666 cubic feet.

To convert from cubic feet to cubic meters, we multiply by 0.028317.
66.6666666*0.028317=1.8878 cubic meters.