301 redirect

Hi,

I’ve built up a demo website on a subdirectory (https://www.a.com/demo) which contains a page https://www.a.com/demo/blog. I have moved this demo website to another domain (www.b.com) which already contains a subdirectory (www.b.com/blog).

I want to redirect the blog installed in the subdirectory of ‘b’ to a page having the same permalink (www.b.com/blog). How can I do it without affecting SEO? The articles in the blog of b website are age-old and I don’t want to lose SEO rank.

I’ve looked into the entire web but couldn’t find a solution for a 301 redirect for the same permalink. I’d really appreciate any kind of help.

Thank you in advance.