I would like to check which page of my website is more relevant to a certain keyword. Can you tell me how to do this? I really need this to promote my resource.

You can do it online using this On-Page SEO Checker - https://pr-cy.io/tools/content-analysis/. It is very convenient in that it evaluates by points each indicator important for the promotion of the site, so you can more accurately assess the effectiveness of optimization of landing pages of your site.