Попробуйте ниже; предполагает, что данные находятся на листе 1, а затем отфильтровывают дополнительные заголовки
let Source = Folder.Files("C:\directory\subdirectory"),
#"Filtered Rows" = Table.SelectRows(Source, each ([Extension] = ".xls")),
#"Pull Data" = Table.AddColumn(#"Filtered Rows", "Data", each Excel.Workbook([Content], null, true){[Item="Sheet1",Kind="Sheet"]}[Data]),
Invert = Table.TransformColumns(#"Pull Data", {{"Data", each Table.Transpose(_)}}),
#"Removed Columns" = Table.RemoveColumns(Invert,{"Content", "Name", "Extension", "Date accessed", "Date modified", "Date created", "Attributes", "Folder Path"}),
MaxColumns = List.Max(List.Transform(#"Removed Columns"[Data], each Table.ColumnCount(_))),
#"Expanded Content" = Table.ExpandTableColumn(#"Removed Columns", "Data", List.Transform({1..MaxColumns}, each "Column" & Number.ToText(_))),
#"Promoted Headers" = Table.PromoteHeaders(#"Expanded Content", [PromoteAllScalars=true])
in #"Promoted Headers"