hey guys... i have a problem., im trying to scale something down but it will only let me do it in 1.0 not in mm what im trying to figure out is.. if 64 of height and i need it to be 35 and 64 = 100 then what is 35?????

hey guys... i have a problem., im trying to scale something down but it will only let me do it in 1.0 not in mm what im trying to figure out is.. if 64 of height and i need it to be 35 and 64 = 100 then what is 35?????