Convert from gallon [US, dry] to hectare meter

Unit Definition (gallon [US, dry])
The gallon [US, dry] is a historic British unit of dry volume still used implicitly in the U.S. In the U.S., the term "gallon" is not used in dry measure, but if it were it would be equal to 1/2 peck, or 4 dry quarts, or 268.8025 cubic inches, or approximately 4.404 884 liters. This unit is the English corn or grain gallon, standardized during the reign of Elizabeth I in the sixteenth century. The earliest official definition of a dry gallon in Britain is a 1303 proclamation of Edward I, where the gallon is defined as the volume of 8 pounds of wheat; the current U.S. "gallon" contains about 7.5 pounds of wheat. Grain gallons have tended to be larger than liquid gallons throughout the history of British units, apparently because they were based on heaped rather than "struck" (leveled) containers. A container in which grain has been heaped above the top will hold as much as 25% more grain, and the traditional corn gallon is in fact 16.4% larger than the wine gallon.

Unit Definition (hectare meter)
The hectare meter is a unit of volume used to measure the capacity of reservoirs, equal to the volume of water one meter deep covering one hectare. The unit is used mostly in British Commonwealth countries, especially India, where it provides a metric unit comparable to the traditional English acre foot. Reservoir capacities are often stated in millions of hectare meters (Mha·m or MHM). One hectare meter equals exactly 10 000 cubic meters or about 8.1071 acre feet.