Lengthy article at: https://www.ers.usda.gov/data-products/foreign-agricultural-trade-of-the-united-states-fatus/documentation/

The only thing relevant to the metric discussion is:

Units of Measure

Trade data released from the U.S. Census Bureau are reported in a range of units of measure. Although value is reported in U.S. dollars, units of volume are varied. The primary units of volume reported in FATUS summary tables include DOZ=Dozen, DS=Doses, KG=Kilogram, KL=Kiloliters, LITER=Liter, LITPF=Proof liter, MT=Metric tons, NO=number, PCS=Pieces, THNDS=Thousands. A more exhaustive list of units comprised in the underlying data can be viewed at Global Agricultural Trade System (GATS). To navigate to Units of Measure, using the top right menu bar select Reference Info > Definitions > Units of Measure.

The symbols are a random made-up abomination, but at least the units are either metric or a physical count (pieces, dozens, thousands). No bushels, short tons, etc.