The US dry gallon is a unit of volume in the US customary unit system with the symbol dry gal.
The dry gallon is equal to 268.8025 in³ or 4.404 L.
The US dry gallon is not used anywhere any more - the unit below is the dry pint and the unit above is the bushel.
The cubic yard is a unit of volume derived from the imperial system of units. It uses the symbol yd³.
It equals the volume of a cube with edges that each measure 1 yard. It is equivalent to 27 ft³, 46656 in³ or ≈ 0.764554 m³.
The yard (and derivatives like the cubic yard for example) are the same in both the imperial systems and US customary systems so require less conversion systems to calculate / convert to SI or metric.