Moving pages of your website to a folder and adjusting the navigation menu to show only inner page links should not necessarily hurt your website's SEO if done correctly. However, it's essential to follow best practices to ensure that search engines can still crawl and index your content effectively. Here are some steps to consider:

• 301 Redirects: If you are changing the URLs of the pages, set up 301 redirects from the old URLs to the new ones. This tells search engines that the content has moved permanently and helps preserve SEO equity.
• Update Internal Links: Make sure that internal links within your website (from other pages, blog posts, etc.) are updated to point to the new URLs.
• XML Sitemap: Update your XML sitemap to include the new URLs. This helps search engines discover and index the new pages more efficiently.
• Robots.txt: Ensure that your robots.txt file does not block search engine crawlers from accessing the new folder and its contents.
• Canonical Tags: Use canonical tags if you have duplicate content issues, indicating the preferred URL for indexing.
• Submit to Search Engines: Resubmit your updated sitemap to search engines (Google Search Console, Bing Webmaster Tools, etc.) to expedite the indexing process.
• Test and Monitor: After making these changes, monitor your website's performance in search results and check for any issues using tools like Google Search Console. Address any errors or problems promptly.
  By taking these steps, you can minimize the impact on SEO and ensure that search engines can still access and index your content effectively.

I focus on these main points when I want to move some pages of my website to a folder and nav menu in those pages should only show inner page links for my Site Pet Nutrition Guru.

It is also help ful when I move the blog (Can Cats Eat Mochi?).

To check the domain age, you can use various online tools and services. One of the commonly used methods is to visit a domain age checker website. Here are the steps to check the domain age:

• Open your web browser and go to a domain age checker website like "whois.net," "who.is," or "domain age checker" (you can find these by searching in your preferred search engine).

• In the search or query box provided on the website, enter the domain name (e.g., petnutritionguru.com) for which you want to check the age.

• Click on the "Search" or "Check" button.

• The website will retrieve information about the domain, including its creation or registration date.

• Look for the "Creation Date" or "Registration Date" in the results. This date represents the domain's age.

Please note that some domain age checker websites may also provide additional information about the domain, such as its expiration date and registrar.

I used these step Whenever I want to check the Domain age of my Website "Pet Nutrition Guru"

Here are some Tools that I used:

Free Keyword Research Tools
Google Keyword Planner
Google Trends
Semrush
Moz

These are working Perfectly from my perspective. What I need they Provide me with almost 95% accurate Results. These are the tools I used to Keyword Research for my Website Pet Nutrition Guru.
It helped me to grow my audience.