In such problems, you should convert everything to the same unit - in this case, to millimeters or to meters. Then it should be easy to compare the two measurements.
0.03m= 0.03x1000= 30mm The longest is 3000mm
The volume of this pipe is 28,510,000 mm3
3000mm = 3 metres
3000mm is 9 feet 10.1 inches.
0.003m = 3.0*10-3 m.
3000mm
118.1102 inches.
3
3m is 3000mm.
3 meters
Divide by 1000.
The longer side is usually called "length".