BuddyPress.org

I have found the answer of your question in this forum after searching 2 days….below is the answer

You’ll have to install donncha’s sitewide tags plugin. It takes all blog posts from all blogs and puts them either on a ‘community’ blog that gets created for that purpose or you can have all blog posts go to the main blog.

https://wordpress.org/extend/plugins/wordpress-mu-sitewide-tags/

I have used that plugin and I could bring all my blog post into the main blog…