Excel formula to power query M code

Hi ppm1 I modified your code to give me that lower case O in the middle, and it goes like this:

let
    input = [columnname],
    letters = {"A".."Z"},
    concatvalues = {null, "A".."Z", "0".."5"},
    splitinput = List.Split(Text.ToList(Text.Upper(input)), 5),
    lettercheck = List.Transform(splitinput, (x)=> List.Transform(x, (y)=> Number.From(List.Contains(letters, y)))),
    multipliers = {1, 2, 4, 8, 16},
    listsums = List.Transform(lettercheck, (a)=> List.Sum(List.Transform({0..4}, (b)=> a{b} * multipliers{b}))),
    listvalues = List.Transform(listsums, each concatvalues{_+1}),
    result = input & Text.Combine(listvalues, "")
in
    result

 Thanks for the help and hope I can come back to you with feedback and more help