Need column in respective arrangement

Here is an example of combining three tables with one similar column and then getting ride of null values.
Starting with...

and end up with...

Paste the code into the advanced editor of a blank query and you can review the steps...

let
    tableOneSource = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcjbUUQgyVNJRCgEynI3AnFgdqLgRsrgRQtwYWdxYKTYWAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [tableOneColumnOne = _t, tableOneColumnTwo = _t]),
    tableTwoSource = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcjbUUQgyVNJRCjHSUXA2AnNidaDiRsjiRghxY2RxY6XYWAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [tableTwoColumnOne = _t, tableTwoColumnTwo = _t]),
    tableThreeSource = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcjbUUQgyVNJRCjHWUXA2AnNidaDiRsjiRghxY2RxY6XYWAA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [tableThreeColumnOne = _t, tableThreeColumnTwo = _t]),
    combineNoRename = 
    Table.Combine(
        {tableOneSource, tableTwoSource, tableThreeSource}
    ),
    renameTableOneColumnOne = 
    Table.RenameColumns(tableOneSource, {"tableOneColumnOne", "ColumnOne"}),
    renameTableTwoColumnOne = 
    Table.RenameColumns(tableTwoSource, {"tableTwoColumnOne", "ColumnOne"}),
    renameTableThreeColumnOne =
    Table.RenameColumns(tableThreeSource, {"tableThreeColumnOne", "ColumnOne"}),
    combineColumnOneRename = 
    Table.Combine({renameTableOneColumnOne, renameTableTwoColumnOne, renameTableThreeColumnOne}),
    groupByColumnOne = 
    Table.Group(
        combineColumnOneRename, 
        {"ColumnOne"}, 
        {
            {"allRows", each _, type table [ColumnOne=nullable text, tableOneColumnTwo=nullable text, tableTwoColumnTwo=nullable text, tableThreeColumnTwo=nullable text]}
        }
    ),
    unpivotNonGroupedColumns = 
    Table.TransformColumns(
        groupByColumnOne, 
        {
            {"allRows", each Table.UnpivotOtherColumns(_, {"ColumnOne"}, "name", "value")}
        }
    ),
    transposeColumns = 
    Table.TransformColumns(
        unpivotNonGroupedColumns, 
        {
            {"allRows", each Table.PromoteHeaders(Table.Transpose(Table.SelectColumns(_, {"name", "value"})))}
        }
    ),
    expandInnerTables = 
    Table.ExpandTableColumn(
        transposeColumns, 
        "allRows", 
        {"tableOneColumnTwo", "tableTwoColumnTwo", "tableThreeColumnTwo"}
    )
in
    expandInnerTables

 Hope this gets you pointed in the right direction.