There are one thousand millimetres in a metre the prefix milli- stands for thousandths. So 0.25 metres is 0.25 x 1000 millimetres, which is 250 mm.
6450 mm
100 mm
3,000 mm
153 mm
180 mm
8500 mm
304.8 mm
135 mm.
760 mm
50.8 mm
1549.3999999983266 mm.
885 mm