Do a Google Search for “Jquery Smooth Scrolling” that’s the exact terms you’ll need to look for when searching for that type of effect. Since the theme doesn’t come with that feature, you’ll have to add it yourself as a customization. I’m sure there are some WordPress plugins that do it automatically for you, but you could also manually do it by adding code in yourself if you want.
Here is an example – https://wordpress.org/plugins/jquery-smooth-scroll/ But you can do a search on Google or WordPress.org if you want more options or plugins.