0,3,6,9,12,15 no of 0's accepted by (000)*
0,4,8,12,16,20 no of 0's accepted by (0000)*
Union of these two we will get..
0,3,4,6,7,8,9,10,11 (by union of above defined two)
After 6 zeros if we add any no of 0's always accepted by the given language..
So it requires 6+1 = 7 minimum no.of states...