IF object_id('tempdb..#yourTable') IS NOT NULL
BEGIN
    DROP TABLE #yourTable;
END;

SELECT id, CAST(ItemId AS XML) AS ItemId
INTO #yourTable
FROM (VALUES(1, '<itemids><itemid>259</itemid><itemid>489</itemid></itemids>'),
            (2, '<itemids><itemid>6834262</itemid><itemid>489</itemid></itemids>'),
            (3, '<itemids><itemid>6603537</itemid></itemids>')
      )a(id, ItemId);

SELECT id, ParamValues.ItemId.value('.','INT') AS ItemId
FROM #yourTable
OUTER APPLY ItemId.nodes('/itemids/itemid') ParamValues(ItemId);