tried to move wordpress up one folder and its gone

basically i had two installations on the same server.. say https://test.domain.com and https://test.domain.com/blog… i wanted to move the content of blog to the main domain… now i made a big mistake.. i tried to drag and drop the contents into the main folder which contained blog… something went wrong and now i get nothing at .com/blog only an Index of /blog/wp-admin

any quick fix for this and apologies in advance for the beginner foul up