Note the following:
1)There are 8 smaller jobs, i.e. selecting each of the eight characters.
2)There are 26 characters in the English alphabet and there are 10 digits. Thus there are 26+10 = 36 different choices for a character occupying the first position from the left. Similarly, for each of the other characters occupying a particular position, there are 36 ways of selecting it after selecting all the characters to the right of it.
3)Thus each of the eight characters can be chosen in 36 ways. So, all the 8 characters of a password can be chosen in 36 × 36 × 36 × ... 8 times = 368 ways. So, there are 368 = 2,821,109,907,456 different possible passwords!