change the label of the 'add to cart' button

-- url of the page with the problem -- : www.zzpsoft.nl
-- HikaShop version -- : 3.4.0
-- Joomla version -- : 3.8.6
-- Browser(s) name and version -- : firefox Quantum 59.0.2

Hello,
I want to change the label of the Add to Cart button.
In Dutch it's "aan winkelwagen toevoegen"
I want to change this into "bestellen"
How can I do this?
Thank you very much
Ciska