(Approximately) ##4046.83 sq.m./acre##
##1## mile ##= 1609.34## meters
(from here on I used a calculator)
##1 sq. mile = (1609.34)^2 = 2589975.24 sq. meters##
##(1 sq. mile)/(640 acres)##
##color(white)(XXX)=(2589975.24 sq. meters)/(640 acres)##
##color(white)(XXX)=(4046.83 sq. meters)/(1 acre)##