There are 10 different digits (0 to 9) and 26 different letters (A to Z).
The design of the password is:
DDLLLD
Where D is a digit and L is a letter.
Assuming any digit or letter can be repeated in the password, there are
10 x 10 = 100 possible outcomes for the two first digits.
Now for the next three letters, we can have 26 x 26 x 26 = 17576 possible outcomes.
The final digit can be one of the 10 possible digits.
Thus, the total number of possible passwords is:
100 x 17576 x 10 = 17,576,000
More than 17 and a half million different passwords