You can access the array index using `${!array[@]}` and the length of the array using `${#array[@]}` e.g.
#!/bin/bash
array=( item1 item2 item3 )
for index in ${!array[@]}; do
echo $index/${#array[@]}
done
Note that since bash arrays are *zero indexed*, you will actually get
0/3
1/3
2/3