If only one peg is permitted per hole, then there is only one distinguishable way, namely all 6 balls, one per hole.
If multiple pegs are permitted in each hole, then you are asking how many ways can I add the numbers from 0 to 6 so that the sum of the numbers is 6:
6,0
5,1
4,2
3,3
4,1,1
3,2,1
2,2,2
3,1,1,1
2,2,1,1
1,1,1,1,2