No. Mass is better. The same amount of mass can occupy different volumes.
the quantity of matter the object contains
No. Mass is the amount of matter in an object, essentially how much "stuff" is in it. In 3-dimentional terms, volume is usually the best term for size.
When used as a size indicator, "nano" means that the object is so small that its size is best expressed in nanometers.
The measurement that best describes the results of a scientific experiment regarding volume would be by using gallons.
If the object is irregular the best way is to measure the volume of water it displaces when you immerse it completely in water.
I would use litres.
Make a mold of the object and then fill the mold with water and measure the volume of the water.
An altitude of a three-dimensional object refers to the vertical height of the object measured from its base to its topmost point. In the context of geometric shapes, such as a prism or pyramid, the altitude is the perpendicular distance from the base to the apex or top face. This measurement is crucial for determining the volume and surface area of the object.
If the object is irregular the best way is to measure the volume of water it displaces when you immerse it completely in water.
Grams (g)
a way to describe how much matter there is in an object.
The best units would be millimetres for the length measurements and millilitres for the volume.