Creating a redirect option for current page url

How should I check if the current page url has an equivalent on other
sites?

WordPress itself has no knowledge of any equivalency between mysite.com/uk/pricing and mysite.com/dk/priser.

If you’re using a multilingual site plugin to build the different language sites, that would be the plugin’s job. But such a multilingual site plugin may very well have the feature you’re trying to build already.

If you’re not using any multilanguage site plugin, you’ll need to develop a scheme to establish the equivalency between the pages yourself.