<div class="admin__field field field-email_attachment3 " data-ui-id="adminhtml-preorder-edit-tab-email-block-fieldset-element-form-field-email-attachment3">…</div> code example
Example: how to put a name on a fieldset
<!--To put a name on a fieldset, simply use the "legend" tag.-->
<fieldset>
<legend>fieldset name</legend>
</fieldset>