How do I find broken links this way?

I found a tool for broken links, https://www.deadlinkchecker.com/website-dead-link-checker.asp

Now it gives me this picture
404 Not Found https://grid.bidswitch.net/ link/href
404 Not Found https://adservice.google.com/ link/href
404 Not Found https://securepubads.g.doubleclick.net/ link/href
403 Forbidden https://cdn.adsafeprotected.com/ link/href

When I click on one, it says 'error, URL not found.'

So, how do I find where the broken link is?
And when I click on link/herf, it takes me to https://www.thesprucepets.com/ Where there are no broken links?

So, where's the broken link? And where's the page that had linked to it? How do I find them?

 

It looks like the destination website permanently moved or no longer exists! So you need cleaning up broken links, otherwise, in this matter, there is nothing to do.

 

Take a look a Ahrefs. They also provide free broken link checker. It will show you all broken links internal + external.

 

Go to Content – Content by Title on the dashboard, and load the page.
All kinds of nonexistent or broken links will trigger the 404 error page.
The next step is to click the “Go” button on the Google Analytics filter page.
Remember that redirecting and fixing broken links is an ongoing process

 

Its true, I use the Broken Link Checker plugin to check broken or inactive links again, this plugin makes it easy for me to delete broken links with one click, this plugin also works automatically checking for broken links.