Formatting links in PowerPoint is more nuanced than on other platforms because presentations are often displayed/projected rather than being distributed electronically.
If a PowerPoint presentation is only going to be displayed to a group, it is acceptable to show the URL of the link on the slide so that people can follow it. However, if a PowerPoint is going to be distributed electronically (e.g. via email or posted on a website), all links should have descriptive clickable text.
How
The following article from Microsoft describes how to add a link to a PowerPoint slide: Add a hyperlink to a slide. The first section of the article describes how to display the link URL, but remember this is only acceptable if the PowerPoint is only being presented live and not distributed electronically.
Verify
For each link in the presentation, you should be able to get some idea of where the link goes based on the clickable text alone, when all other text and images are removed.