We have 6 people, 3 men, and 3 women.

On how many ways, can we sat them at aroundtable, on 6 chairs, but they must sit in this order: man, woman,man,woman... So the neighbour must be the opposite sex.

Is this correct?

the six in the denominator is because it's aroundtable, and we can rotate them for one place, and would be the same so it's 6 for six places.