Combine multiple files in Power query editor

Based on your screenshot,

a) Change the "Transform file" query M code, as below code (Power Query Window > Home tab > Advanced Editor)

let
    Source = (Parameter1) => let
        Source = Csv.Document(Parameter1,[Delimiter=",", Columns=3, Encoding=1252, QuoteStyle=QuoteStyle.None]),
        #"Added Index" = Table.AddIndexColumn(Source, "File Index", 1, 1, Int64.Type)
    in
        #"Added Index"
in
    Source

b) Change the "PowerBI" query M code , ... in the advanced editor

  delete all lines from this line #"Invoke Custom Function1" till the end and copy the below code. This will give the lines you want.

FYI, I also removed empty data lines , as it wont be of any use

    #"Invoke Custom Function1" = Table.AddColumn(#"Filtered Hidden Files2", "Transform File", each #"Transform File"([Content])),
    #"Removed Other Columns1" = Table.SelectColumns(#"Invoke Custom Function1", {"Name", "Transform File"}),
    #"Expanded Transform File" = Table.ExpandTableColumn(#"Removed Other Columns1", "Transform File", {"Column1", "Column2", "Column3", "File Index"}, {"Column1", "Column2", "Column3", "File Index"}),
    #"Changed Type" = Table.TransformColumnTypes(#"Expanded Transform File",{{"File Index", Int64.Type}}),
    #"Added Conditional Column" = Table.AddColumn(#"Changed Type", "Custom", each if Text.Contains([Column1], "Pid") then "Table 1 Row 1" else if Text.Contains([Column1], "Order placed") then "Table 2 begin" else null),
    #"Duplicated Column" = Table.DuplicateColumn(#"Added Conditional Column", "Custom", "Custom - Copy"),
    #"Sorted Rows" = Table.Sort(#"Duplicated Column",{ {"Name", Order.Ascending}, {"File Index", Order.Ascending}}),
    #"Filled Down" = Table.FillDown(#"Sorted Rows",{"Custom"}),
    #"Filtered Rows3" = Table.SelectRows(#"Filled Down", each ([Custom] = "Table 1 Row 1")),
    #"Trimmed Text" = Table.TransformColumns(#"Filtered Rows3",{{"Column1", Text.Trim, type text}, {"Column2", Text.Trim, type text}, {"Column3", Text.Trim, type text}}),
    #"Filtered Rows4" = Table.SelectRows(#"Trimmed Text", each ([Column1] <> null and [Column1] <> "") and ([#"Custom - Copy"] = null)),
    #"Renamed Columns" = Table.RenameColumns(#"Filtered Rows4",{{"Column1", "Pid"}, {"Column2", "Pname"}, {"Column3", "Amt"}, {"Name", "Source"}}),
    #"Removed Other Columns" = Table.SelectColumns(#"Renamed Columns",{"Source", "Pid", "Pname", "Amt"}),
    #"Reordered Columns" = Table.ReorderColumns(#"Removed Other Columns",{"Pid", "Pname", "Amt", "Source"})
in
    #"Reordered Columns"