Hey there! :)
(1) I would say bar graph because on bar graphs, you can separate all the data into different bars and compare all the different data.
(2) For finding mean, you have to add all the numbers and divide by how many numbers there are.
0 + 1 + 2 + 3 + 4 + 5 + 6 = 21
There are 7 numbers.
21 ÷ 7 = 3
The mean is 3
Hope this helps :)