Merging 2 wordpress installs into 1

I have an interesting problem someone might be able to help out with.

Some years ago, knowing very little about WordPress, I attempted to set up a site, I think it was my first.

For reasons which I can’t even remember now I set it up with a wordpress install on the root, and then made a “blog” folder and set up another wordpress install in that folder.

The root install just has 6 or 7 pages. The “blog” install has only posts, and the urls are domain.com/blog/post

I would like to amalgamate them into one install. I have been wondering if I can do so by exporting the posts from the second install and importing them into the first. The problem is that it will, I expect, change the url structure of the posts. The pages won’t be affected.

Can anybody think of a way that I can amalgamate the 2 installs into 1 without changing the url structure of the posts in the second install?

Many thanks
Peter