Ok so every 2m= 1cm. So you have to divide your side lengths (4 and 6) by 2m in order to find out how many centimetres. 4/2 is 2 and 6/2 is 3 so you have side lengths of 2com and 3cm.
So your lengths was 6m, now it’s 3cm.
And you width was 4m, now it is 2cm