Definition: In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Input: ['U', '1531', 't', '6929', 'P', '9619', 'G', 'g', '8511']

21, 1531, 20, 6929, 16, 9619, 7, 7, 8511