Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
Convoys ONS 18/ON 202
Table title:
Tables
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Date </th><th colspan=1 rowspan=1 > Name </th><th colspan=1 rowspan=1 > Nationality </th><th colspan=1 rowspan=1 > Casualties </th><th colspan=1 rowspan=1 > GRT </th><th colspan=1 rowspan=1 > Sunk by... </th></tr>
<tr> <td colspan=1 rowspan=1 > ONS 18 </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td></tr>
<tr> <td colspan=1 rowspan=1 > 23 September 1943 </td><td colspan=1 rowspan=1 > Steel Voyager </td><td colspan=1 rowspan=1 > United States </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 6,198 </td><td colspan=1 rowspan=1 > U-952 </td></tr>
<tr> <td colspan=1 rowspan=1 > ON 202 </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td><td colspan=1 rowspan=1 > ... </td></tr>
<tr> <td colspan=1 rowspan=1 > 19/20 September 1943 </td><td class="highlighted"  colspan=1 rowspan=1 > Theodore Dwight Weld </td><td colspan=1 rowspan=1 > United States </td><td colspan=1 rowspan=1 > 33 </td><td colspan=1 rowspan=1 > 7,176 </td><td class="highlighted"  colspan=1 rowspan=1 > U-238 </td></tr>
<tr> <td colspan=1 rowspan=1 > 20 September 1943 </td><td class="highlighted"  colspan=1 rowspan=1 > Frederick Douglass </td><td colspan=1 rowspan=1 > United States </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 7,176 </td><td class="highlighted"  colspan=1 rowspan=1 > U-238, U-654 </td></tr>
<tr> <td colspan=1 rowspan=1 > 23 September 1943 </td><td colspan=1 rowspan=1 > Fort Jemseg </td><td colspan=1 rowspan=1 > United Kingdom </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 7,134 </td><td colspan=1 rowspan=1 > U-238 </td></tr>
<tr> <td colspan=1 rowspan=1 > 23 September 1943 </td><td colspan=1 rowspan=1 > Oregon Express </td><td colspan=1 rowspan=1 > Norway </td><td colspan=1 rowspan=1 > 8 </td><td colspan=1 rowspan=1 > 3,642 </td><td colspan=1 rowspan=1 > U-238 </td></tr>
<tr> <td colspan=1 rowspan=1 > 23 September 1943 </td><td colspan=1 rowspan=1 > Skjelbred </td><td colspan=1 rowspan=1 > Norway </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 5,096 </td><td colspan=1 rowspan=1 > U-238 </td></tr>
</table>
Question:
What was the destructive power of the U-238 convoy? 
Answer:
U-238 sunk 2 ships which are Theodore Dwight Weld and Frederick Douglass.