On Twitter, Google’s John Mueller confirmed that you should use a 301 redirect if the new page is a replacement for an old page.
For example, if you had a page about ‘blue widgets’ with the URL old-page.html and now you have a page about ‘blue widgets’ with the new URL new-page.html, then you can use a 301 redirect to redirect old-page.html to new-page.html.
Here’s John Muellers tweet:
301-redirecting for 404s makes sense if you have 1:1 replacement URLs, otherwise we'll probably see it as soft-404s and treat like a 404.— John ☆.o(≧▽≦)o.☆ (@JohnMu) 25. Juni 2017
How to find redirects on your website
Among many other things, the website audit tool in SEOprofiler also finds redirects on your web pages. If you haven’t done it yet, try SEOprofiler now: