Hi,
These options where added in 1.5.6.
If you don't have them on your 2.5.1, it means that you're not using the latest version but the one before.
First, go in the menu Components->HikaShop->Update/About us in your 2.5.1 back end and make sure that you have the latest version, 1.5.6
If not, update.
If it says that you have 1.5.6, then it means that you had a problem during the update to 1.5.6 on your 2.5.1 website. In that case, the best is to change the 'version' entry of the table jos_hikashop_config to 1.5.5, and try to install again the new version. That will trigger the whole update process again.