All the serials are hexadecimal – this means they only contain characters from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 (zero to nine), and A, B, C, D, E, F (ay to eff)- so there are no letters I (eye), O (oh), or L (el).
The key is in a format something like this
A0A0A-0A0A0-A0A0A-0A0A0-A0A0A-0A0A0
(not necessarily letter, number letter, etc, but 6 groups of 5 characters)