The answer depends on 12 WHAT!
None, since there are no such measures as millameters nor centameters. However, 12 millimetres equals 1.2 centimetres.
3 centimetres = 30 millimetres, not millameters.
There are 1 centimetres in 10 millimetre, none in 10 millameters.
1000.
None.However, a millimetre is a thousandth of a metre.
10 millimetres = 1 centimetre.
50mm = 5cm
1 millimetre = 0.1 centimetre.
1 decimetre = 100 millimetres.
1 foot = 304.8 millimetres.
1 centimetre = 10 millimetres.
1 kilometre = 1000000 millimetres.