The breadcrumb can reduce the number of actions a visitor needs to take in order to navigate to a higher-level page, and improve the discoverability of your store.
To show Prev/Next and Back to Collection buttons, you need to go Theme settings > Product Items > Enable 'product url has link collection'.
Note: The Collection name and prev/next buttons only show when you access product by collection link, please check video below to know when it works:
In Theme customize, go to the Product page > Default product > On the left sidebar, you guys will see the Breadcrumb option here:
Show breadcrumb checkbox: Check/ uncheck this checkbox to enable/disable the breadcrumb.
Show back/next product links checkbox: Tick on this checkbox to show previous/ next product if you open the single product page from a Collection page.
When you go to the Single product page via the Collection page, the previous/ next product option will show like the image below:
Moreover, you can change the Background color, Link color.