Step 1. Convert grams to tonnes
#1 color(red)(cancel(color(black)("g"))) × (1 color(red)(cancel(color(black)("kg"))))/(1000 color(red)(cancel(color(black)("g")))) × ("1 t")/(1000 color(red)(cancel(color(black)("kg")))) = 1 × 10^"-6"color(white)(l) "t"#
Step 2. Convert cubic centimetres to cubic metres
#1 color(red)(cancel(color(black)("cm")))^3 × (("1 m")/(100 color(red)(cancel(color(black)("cm")))))^3 = 1 × 10^"-6"color(white)(l) "m"^3#
Step 3, Calculate the density in the new units
#D = (2.5 color(red)(cancel(color(black)("g"))))/(1 color(red)(cancel(color(black)("cm"^3)))) × (1 × color(red)(cancel(color(black)(10^"-6"))) "t")/(1 color(red)(cancel(color(black)("g")))) × (1 color(red)(cancel(color(black)("cm"^3))))/(1 × color(red)(cancel(color(black)(10^"-6"))) "m"^3) = "2.5 t/m"^3#
Step 4. Calculate the volume
#V = T color(red)(cancel(color(black)("t"))) × ("1 m"^3)/(2.5 color(red)(cancel(color(black)("t")))) = 0.40Tcolor(white)(l) "m"^3#