Hi,
First, you need to go to the HikaShop menu Display->Views and search for the file listing_price of the view product and edit it. Then, add the code
if(!empty($this->element->product_id) && isset($this->row->product_weight) && bccomp($this->row->product_weight,0,3)){
$weight_price = $price->price_value_with_tax / $this->row->product_weight;
echo JText::_('PRICE_SEPARATOR').$this->currencyHelper->format($weight_price,$price->price_currency_id).' / '.JText::_($this->row->product_weight_unit);
}
just before the code
}
echo JText::_('PRICE_END');
near the end of the file.
That will display the price relative to the product weight and the product unit on the product page. So if you have a weight of 0.75kg, that will display the price for 1kg.
Then, you can go to the configuration under the tab languages and edit your HikaShop translation file.
There, you can add a line like this:
KG="Liter"
You can do that for each language so that you can translate the unit in each language you use on your website.