a lookup formular in convert my daily data into monthly data

Power Query

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Result:", type date}, {"Numbers", Int64.Type}}),
    #"Calculated Start of Month" = Table.TransformColumns(#"Changed Type",{{"Result:", Date.StartOfMonth, type date}}),
    #"Grouped Rows" = Table.Group(#"Calculated Start of Month", {"Result:"}, {{"Count", each List.Max([Numbers]), type number}})
in
    #"Grouped Rows"