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: ['6921', 'y', '3837', 'j', 'u', 'q', 'v', 'u', '2867', 'T', '9629', 'L', '3753']

6921, 25, 3837, 10, 21, 17, 22, 21, 2867, 20, 9629, 12, 3753