Study the two different positions of a cube given below with dots from 1 to 6 marked on its faces. When 3 is at the bottom, what will be at the top?

As per the given pattern in question figure , we can find the similar next position of given dice .
Here 2 and 4 dots are at the same side .
From figure 2 and 4 are adjacent to both 3 and 6 hence 6 will be opposite to 6. '3' lies opposite '6'.