How to Set up a URL Redirect for Fixing “404 page not found” Error on Shopify

You should use redirection for that missing URL.

From your Shopify admin, go to Online Store > Navigation.
Click URL Redirects.
Click Add URL redirect.
In Redirect from, enter the old URL you want to redirect visitors from. Only broken URLs should be redirected. If the old URL still loads a webpage, the URL redirect won’t work.
Note: You can’t redirect URLs that begin with the following prefixes: /apps, /application, /cart, /carts, /orders, /shop, or /services.
In Redirect to, enter the new URL that you want to redirect visitors to. If you want to redirect to your store’s home page, then enter /.
Note: The new URL can be either a relative URL (for example, /collection/shirts) or a full URL (for example, To redirect traffic within your primary domain, use a relative URL. To redirect outside your primary domain, use a full URL.
Click Add.

And that’s it.