This feature is a part of Product Page Customizer. Click here to see all Product Page Customizer features.
To show Next & Previous Product URLs on the top of product page please find the Product Settings > Catalog Design > Product Page settings page. You will see there Product Page Elements and Next & Previous product URLs on top checkbox in it.
After you check the checkbox the Next & Previous product URLs will appear on the top of each product page. The design will match your theme style but it will look similar to this:
