Google crawler should be able to index your blog posts eventually. You don’t have to submit it. But it is recommended to submit your blogspot blog sitemap to Google Search Console. It might help you get your posts or pages indexed in Google quicker.
For this, you don’t need any custom sitemap for Blogger blog. Sitemap is automatically generated by Blogger.
For posts:
http://blog-name.blogspot.com/sitemap.xml
http://custom-domain.com/sitemap.xml
For pages:
http://blog-name.blogspot.com/sitemap-pages.xml
http://custom-domain.com/sitemap-pages.xml
If you are using custom domain name, you need to use custom domain urls mentioned above. You can check urls for your blog in the browser & submit them in Google Search Console. If you don’t have pages in your blog, then don’t submit sitemap for pages.