That extension does not apparently supports HikaShop:
extensions.joomla.org/extensions/access-...authentication/10343
On their page, they say that they can add that for you for free.
So you should ask them about that.
There is no email confirmation field in HikaShop. We'll add that in next release. In the mean time, you would have to edit the file "registration" of the view "user" via the menu Display->Views and add the code:
<tr class="hikashop_registration_email_confirm_line">
<td class="key">
<label id="email_confirm_msg" for="register_email_confirm">
<?php echo JText::_( 'HIKA_EMAIL_CONFIRM' ); ?>
</label>
</td>
<td>
<input type="text" id="register_email_confirm" name="data[register][email_confirm]" value="<?php echo $this->escape($this->mainUser->get( 'email' ));?>" class="inputbox required validate-email" maxlength="100" onchange="if(this.value!=document.getElementById('register_email').value){alert('<?php echo JText::_('THE_CONFIRMATION_EMAIL_DIFFERS_FROM_THE_EMAIL_YOUR_ENTERED',true); ?>'); this.value = '';}" /> *
</td>
</tr>
and the translations THE_CONFIRMATION_EMAIL_DIFFERS_FROM_THE_EMAIL_YOUR_ENTERED and HIKA_EMAIL_CONFIRM via the languages tab of the configuration.