JSFiddle - React, Tailwind, and code Playground

HTML

<table class="ms-formtable">
  <tbody>
    <tr>
      <td nowrap="true" valign="top" width="113px" class="ms-formlabel">
        <h3 class="ms-standardheader"><nobr>Thank you</nobr></h3>
      </td>
    </tr>
    <tr>
      <td nowrap="true" valign="top" width="113px" class="ms-formlabel">
        <h3 class="ms-standardheader"><nobr>Thank you</nobr></h3>
      </td>
    </tr>
      <tr>
      <td nowrap="true" valign="top" width="113px" class="ms-formlabel">
        <h3 class="ms-standardheader"><nobr>Thank you</nobr></h3>
      </td>
    </tr>
      <tr>
      <td nowrap="true" valign="top" width="113px" class="ms-formlabel">
        <h3 class="ms-standardheader"><nobr>Thank you</nobr></h3>
      </td>
    </tr>
      <tr>
      <td nowrap="true" valign="top" width="113px" class="ms-formlabel">
        <h3 class="ms-standardheader"><nobr>Thank you</nobr></h3>
      </td>
    </tr>
    <tr>
      <td nowrap="true" valign="top" width="113px" class="ms-formlabel">
        <h3 class="ms-standardheader"><nobr>Thank you</nobr></h3>
      </td>
    </tr>    
  </tbody>
</table>

JavaScript

$('table.ms-formtable > tbody > tr:nth-child(4) td:nth-child(1) h3').replaceWith(function() {
    return $('<h1>', {
        'class': this.className,
        'html':  this.innerHTML
    });
});