Move the buttom under available product in product page

-- HikaShop version -- : 3.1.0
-- Joomla version -- : 3.7.1

Hello
I wuold like move the buttom under the text "Prodotto disponibile" in the list product page:
goo.gl/MmasW2

In the site with old version of hiksahop I solved with this css:
/* portato il bottono sotto la scritta prodotto disponibile e centrato */
#hikashop_product_stock .btn .hikashop_product_stock a.hikashop_cart_button, .hikashop_product_stock .btn.button.hikashop_cart_input_button, .hikashop_product_stock a.hikashop_cart_button {
display: block;
margin: 0 auto;
width: 100px;
}
.hikashop_subcontainer .hikashop_product_stock_count a.hikabtn a.hikacart {
display: block;
margin: 0 auto;
width: 100px;
}
You can see here in cation:
goo.gl/46bVhh
But now it doesn't work
HOw can I solve??

Thanks FRank