DECLARE @Columns TABLE (ColumnOrder INT, ColumnName varchar(20), StartingPosition smallint, ColumnSize tinyint);
INSERT INTO @Columns
SELECT 1, 'Column1', 1, 10 UNION ALL
SELECT 2, 'Column2', 11, 5  UNION ALL
SELECT 3, 'Column3', 16, 12;

DECLARE @TestData TABLE (RowID INT IDENTITY, RowData varchar(100));
INSERT INTO @TestData
SELECT 'y4gfbnenbeofnoihfgjq3fgwqgnq3ovqvqno' UNION ALL
SELECT 'qgbughqofniufgonqgoinvoqfqnbqnqn3qfo';

WITH cte AS
(
SELECT t.RowID, dt.*
  FROM @TestData t
       CROSS APPLY (SELECT ColumnOrder, 
                           ColumnName, 
                           ColumnValue = SubString(t.RowData, StartingPosition, ColumnSize)
                      FROM @Columns) dt
)
SELECT RowID,
       Column1 = MAX(CASE WHEN ColumnName = 'Column1' THEN ColumnValue ELSE NULL END),
       Column2 = MAX(CASE WHEN ColumnName = 'Column2' THEN ColumnValue ELSE NULL END),
       Column3 = MAX(CASE WHEN ColumnName = 'Column3' THEN ColumnValue ELSE NULL END)
  FROM CTE
 GROUP BY RowID
 ORDER BY RowID;