Unpivoting challenge (multiple Excel files with multiple spreadsheets from a Sharepoint folder)

Thank you wdx223_Daniel ,

it does work, but the result is not exactly what I expected.

I adapted your code in this way:

let
    Source = SharePoint.Files("my Sharepoint path", [ApiVersion = 15]),
    #"Filtered Rows" = Table.SelectRows(Source, each Text.StartsWith([Name], "my text filter")),
    custom1=Table.Combine(List.TransformMany(#"Filtered Rows"[Content],each Excel.Workbook(_)[Data],(x,y)=>Table.UnpivotOtherColumns(y,{"Column1","Column2","Column3"},"End of Mounth","Value")))
in
    custom1

and this is the result

At the end I solved my need with the following solution

let
    Source = SharePoint.Files("my Sharepoint url", [ApiVersion = 15]),
    #"Filtered Rows" = Table.SelectRows(Source, each Text.StartsWith([Name], "my text filter")),

    WorkbookList = List.Transform(#"Filtered Rows"[Content], each Excel.Workbook(_)[Data]),
    SpreadsheetList = List.Combine(WorkbookList),

        TransformTable = (SpreadsheetList as list) as list => 
    let
        TransformedTable = List.Transform(
            SpreadsheetList, each 
                Table.UnpivotOtherColumns(
                    Table.PromoteHeaders(_, [PromoteAllScalars=true]),
                    {"Col1", "Col2", "Col3"},
                    "Attribute", "Value"))
    in
    TransformedTable,

    SpreadsheetTable = Table.Combine(TransformTable(SpreadsheetList))

in
    SpreadsheetTable

Thank you again wdx223_Daniel for your answer, because helped me to understand better iterations in M, you deserve a Kudos!

m