Extracting a Specific string format from a string of text

Hello agc1234,
same result as Vijay_A_Verma but different approach.

See line four. This one also matches the criteria.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("LY4xCwIxDEb/SuhsoU3StHVrFRyELi5C7aBww8G5nNz/V68dX/Lge7Uqa5IweVTtUNWtGDwFMUwdp3V+LlC292taYf7AESxdY0Tiof8OsZCw8xLgsRmDAhYvLvi7+N2xAgkkkPQFRJ29Cxw7WZ2ZNDvprtlT8nnQvyyNtDSeqrUv", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Serial #" = _t]),
    UppercasedText = Table.TransformColumns(Source,{{"Serial #", Text.Upper, type text}}),
    Ad_Cleaned = Table.AddColumn(UppercasedText , "Cleaned", each Text.Select([#"Serial #"], List.Buffer({"0".."9", "A".."Z"}))),
    Ad_EachFourCombination = Table.AddColumn(Ad_Cleaned, "Each 4 Combination", each List.Accumulate( 
    {0..Text.Length([Cleaned])-1},
    {},
    (s,c)=> List.RemoveNulls(s & { try Text.Range([Cleaned], c, 4) otherwise null })
), type list),
    Ad_OnlyMatching = Table.AddColumn(Ad_EachFourCombination, "Only Matching", each List.RemoveNulls(List.Transform([Each 4 Combination], each 
      if  (try Value.Is(Number.From(Text.ToList(_){0}), Number.Type) otherwise false) //1st digit check if is number
      and (try Value.Is(Number.From(Text.ToList(_){1}), Number.Type) otherwise false) //2nd digit check if is number
      and (try not Value.Is(Number.From(Text.ToList(_){2}), Number.Type) otherwise true) //3rd digit check if is text
      and (try Value.Is(Number.From(Text.ToList(_){3}), Number.Type) otherwise false) //4th digit check if is number
      then _ else null)), type list),
    Ad_FourDigits = Table.AddColumn(Ad_OnlyMatching, "4 digits", each Text.Combine([Only Matching], ", "), type text),
    RemovedOtherColumns = Table.SelectColumns(Ad_FourDigits,{"Serial #", "4 digits"})
in
    RemovedOtherColumns