my older site was built with older version of sitebuilder on a pc so I don't know how to adjust for mobile view

It sounds like your older site was/is built on desktop or SiteBuilder Plus and the new site you built on the new Websitebuilder.  The newer version is a responsive builder and offers the ability to create a site that will render correctly depending on the device it is being viewed on; smart phones, lap tops, tablets, etc. The older version doesn't have that capability. You can use Duda Mobile or you can rebuild the old site with the newer Websitebuilder. I'd highly recommend switching to the new builder as Duda Mobile doesn't always incorporate edits properly, it's free if you don't mind their ads and limited options and having to deal with essentially two sites, whereas the new builder is all-in-one. The drawback to it is that you have to rebuild your site as the software between it and the new one is so different that you can't just copy it over. But, you can leave your existing site up and functional while you are building the new one.
A long-winded reply, but wanted you to know the options. :)