Well, it worked for me, but the info I found was a little confused, so I'm going to detail the steps I did.
1. Create the article for Terms and Conditions.
2. Create a Menu Item of type 'Simple Article' and link it to the article Terms and Conditions.
3. Now you can configure the parameters for the menu item for not showing the word 'Articles' (if this config is not the same as Global)
4. Edit the file ‘terms’ of your front end template (access from Hikashop->Display->Views) and replace the line:
$text = '<a href="'.JRoute::_('index.php?option=com_content&view=article&id='.$terms_article.'&tmpl=component').'" class="modal" rel="{handler: \'iframe\', size: {x: 450, y: 480}}" target="_blank">'.$text.'</a>';
by:
$text = '<a href="'.JRoute::_('index.php?option=com_content&view=article&id='.$terms_article.'&Itemid=8&tmpl=component').'" class="modal" rel="{handler: \'iframe\', size: {x: 450, y: 480}}" target="_blank">'.$text.'</a>';
(Add &Itemid=8 before &tmpl=component), where 8 is the ID of the menu item that you have just created.
With these steps it may work. My error was that I created a menu item but I didn't link it to the article Terms and Conditions, and browser couldn't show anything, only a 404 error.
I hope these steps will help somebody.
Thanks.