How can I create this table or matrix?

Ok Anonymous - here is the Power Query version. It returns a hastily prepared matrix that looks like this:

I created Table C, which was your Table B, but modified. The M code to do this is as follows:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjOwNDCx0DU0sARiJR0lCyA2N1KK1cGUMjIEEobG2CWNjUGSBjgkTfDotDDDI2lpDiTMDJRiYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Item = _t, #"Pallet ID" = _t, #"Pallet Pcs" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Item", type text}, {"Pallet ID", Int64.Type}, {"Pallet Pcs", Int64.Type}}),
    #"Added Enough Pieces" = 
        Table.AddColumn(
            #"Changed Type", 
            "Enough Pieces", 
            each
                let 
                    varItemNeeded = [Item],
                    varPalletId = [Pallet ID],
                    varPiecesNeeded = Table.SelectRows(#"Table A", each [Item] = varItemNeeded)[Pcs to complete request]{0}
                in
                List.Sum(
                    Table.SelectRows(#"Changed Type", each [Pallet ID] <= varPalletId)[Pallet Pcs]
                ) > varPiecesNeeded,
                type logical
        ),
    #"Added Pallet Needed" = 
        Table.AddColumn(#"Added Enough Pieces", "Pallet Needed", 
        each 
            let
                varLastPallet = 
                    List.Min(
                        Table.SelectRows(#"Added Enough Pieces", each [Enough Pieces] = true)[Pallet ID]
                    )
            in
            [Pallet ID] <= varLastPallet,
            type logical
        ),
    #"Filtered Rows To Keep What Is Needed" = Table.SelectRows(#"Added Pallet Needed", each ([Pallet Needed] = true)),
    #"Removed Other Columns" = Table.SelectColumns(#"Filtered Rows To Keep What Is Needed",{"Item", "Pallet ID", "Pallet Pcs"})
in
    #"Removed Other Columns"

Before filtering and removing columns, it returns this table in Power Query:

I want to keep the three rows in red. The next two steps just filter for that, then keeps only the first 3 columns.
I did the Enough Pieces and Pallets Needed in two columns because it is Friday afternoon and getting all of that logic in one column was making my head hurt this late in the week. 😁

I make no warrants however on the performance of the M code on a large (100K or larger) record set. And I hate the matrix I created, but now that you have a table to link to, you can format it or display it however you like.

Here is the PBIX file.

Please mark one or both as the solution if they help. Or tell me I am off my rocker and totally missed your objective! 
To adapt the M code to your model...
1) In Power Query, select New Source, then Blank Query
2) On the Home ribbon, select "Advanced Editor" button
3) Remove everything you see, then paste the M code I've given you in that box.
4) Press Done
5) See this article if you need help using this M code in your model.