What’s the measurement for soil quantity in Science?
the metric system is more appropriate for science. Still a lot of use of the standard US system in Engineering in the US, but the rest of the world is metric. I do not know what you are testing, so I don't know if weight in grams/kilograms is good enough for your purpose or whether there might be some use in also knowing the volume (in liters/ml or in cubic cm), but I think what your teacher wants is the use of metric units. meters liters grams rather than feet gallon pound. There is not really anything "wrong" with your use of standard units, because you can easily convert them to metric (you would not need to reweigh). You should report in metric units though. Use appropriate rounding/precision, of course. You should ask your teacher what he/she means by "wrong". Did she mean you used the wrong measurement system (wrong units) or that you made the wrong measurement (measured weight when volume was what was expected)? It isn't very useful to just tell someone they are wrong without giving some idea of what is right.
I don't see what's the matter with ounces, but grams and kilograms are the usual "science" units. Did you weigh the soil, or did you measure the volume? Weighting is better. 1 ounce = 28.35 grams.