I had to write a little bit of PHP to convert mm into feet and inches.
$mm_value = 2590.00;
$convert_to_metres = floor($mm_value) / 1000;
$convert_to_inches = $convert_to_metres * 39.3701;
$feet_value = floor( $convert_to_inches / 12 );
$inches_value = ( $convert_to_inches % 12 );
print $feet_value . '\' ' . $inches_value . '"';
Should give you 8’ 5” ;)