Sitemap Generation

As per your post, your website is on ecommerce then it was definitely develop on word-press or framework like Magneto then you need not worry about that and just add plugin like "SEO Jet pack" etc.

Best practices if you want to enable a sitemaps

If you don’t have a sitemap yet, we recommend first that you explore if your web site or your CMS can manage this, or install a sitemap plugin.

If you have to, or want to, develop your own sitemaps, we suggest the following best practices:

1.First, follow the sitemaps reference at www.sitemaps.org. Common mistakes we see are people thinking that HTML Sitemaps are sitemaps, malformed XML Sitemaps, XML Sitemaps too large (max 50,000 links and up to 10 megabytes uncompressed) and links in sitemaps not correctly encoded.

2.Have relevant sitemaps linking to the most relevant content on your sites. Avoid duplicate links and dead links: a best practice is to generate sitemaps at least once a day, to minimize the number of broken links in sitemaps.

3.Select the right format:
1.Use RSS feed, to list real-time all new and updated content posted on your site, during the last 24 hours. Avoid listing only the past 10 newest links on your site, search engines may not visit RSS as often as you want and may miss new URLs. (This can also be submitted inside Bing Webmaster Tools as a Sitemap option.)

2.Use XML Sitemap files and sitemaps index file to generate a complete snapshot of all relevant URLs on your site daily.

4.Consolidate sitemaps: Avoid too many XML Sitemaps per site and avoid too many RSS feeds: Ideally, have only one sitemap index file listing all relevant sitemap files and sitemap index files, and only one RSS listing the latest content on your site.

5..Use sitemap properties and RSS properties as appropriate.

6.Tell search engines where our sitemaps XML URLs and RSS URLs are located by referencing them in your robots.txt files or by publishing the location of your sitemaps in search engines’ Webmaster Tools.

Hello there can you please share site url

Hello There,
You can use the any site map generator, also search on Google then choose what type of tools you can check online.

Thanks

Now, there are lots of free sitemap generators available on internet. Just enter your website, they generate sitemap for you. You don't need to worry about how many pages your website has.

The problem is, most site map generators do not allow 10,000+ URLS.

The good news is, most sites do not need a sitemap at all. They provide little benefit to 99% of websites.

If you absolutely MUST have a sitemap for whatever reason, it would be best to break your site up into several sitemaps - maybe starting at the category level with a general sitemap that points to the individual category sitemaps, as well.

The easiest way is definitely a plugin if you're using wordpress etc. It will generate one for you. You can then download it if you want to and submit it to google if needed.