Calculators volume 40 square meters by 100 milimeters

You don't. Cubic meter is a measure of volume while square meter is a measure of volume.

For example, consider a room that's ten meters by ten meters, The room is 100 square meters. Now consider a ceiling that's two meters high. The volume is 200 cubic meters. Then raise the ceiling a meter so it's three meters high. Now the volume is 300 cubic meters, while the area is still 100 square meters.

Multiply the length by the depth to get 100 meters squared.

15 square meters times 7 meters is 105 cubic meters.

You don't. Square feet is a measure of area while cubic meters is a measure of volume.

Consider a room 8 ft by 10 ft. The floor area is 80 square ft. What's the volume of the room in cubic feet (let's not worry about converting to meters yet). Well, that depends on the height of the ceiling, doesn't it? If the ceiling is 8 ft high then the volume is 640 cubic feet. If the ceiling is 12 ft high then the volume is 960 cubic feet. Without that third dimension, you can't calculate the volume.

Simply square the conversion factor between feet and metres to get the conversion factor between square feet and square metres.

One foot is 0.3048 metres, so squaring that gives one square foot is 0.09290304 square metres.

By definition one hectare is 100 meters squared or 10000 square meters. Thus 0.02 hectares is 200 square meters.

I am sorry to say it but your units do not make sense: Units of volumes and areas are mixed up.
Let us try to make sense of it.
If you have some container whose base is 3 square meters (not cubic meter sq) and it has a height of 3 inches you can calculate its volume in cubic meters or in cubic inches or cubic feet. To do so convert the height in inches into meters and multiply the area of the base by the height in meters and you will obtain the volume in cubic meters. To get the volume in cubic inches convert the area of the base to square inches and multiply by the height in inches.

However, even after you have expressed the volume in one unit or another (m^3 or in^3) you cannot find the mass of the substance contained (be it in tons, tonnes or kilograms): You need to know the substance and more specifically its density or its specific gravity).
Please, reformulate your question and specify the substance that fills or would fill the volume. Without that information, nothing doing.

That is something that cannot be done (cubic to square). You can convert cubic meters to cubic feet or square meters to square feet as follows:

Multiply cubic meters by 35.3146 to get cubic feet

Multiply square meters by 10.7639 to get square feet

One foot is 0.3048 meters. One square foot is 0.3048^2 meters = 0,9290304m^2. Multiply that by the area in square feet which is 100ft*150ft = 15000 ft^2.

The result is 1393.5456m^2