with dat as (select xmltype('<xmlas>
<CreDtTm>2018-10-11T07:36:49</CreDtTm>
<Orders>
 <Id>985</Id>
 <Item><Amt>15.00</Amt></Item>
 <Item><Amt>63.00</Amt></Item>
</Orders>
<Orders>
 <Id>145</Id>
 <Item><Amt>11.00</Amt></Item>
 <Item><Amt>97.00</Amt></Item>
 <Item><Amt>45.00</Amt></Item>
</Orders>
</xmlas>' ) x from dual )
select xtbl.amt
from dat, xmltable('/xmlas/Orders/Item'
passing dat.x columns
amt varchar2(100) path 'Amt'
) xtbl

Amt    ID   CreDtTm
15.00  985  2018-10-11T07:36:49
63.00  985  2018-10-11T07:36:49
11.00  145  2018-10-11T07:36:49
97.00  145  2018-10-11T07:36:49
45.00  145  2018-10-11T07:36:49