Folders

First of all, are you using Lightroom Classic or Lightroom? Those are two different applications. If you imported the photos in Lightroom, then this makes sense. Lightroom stores images in the cloud. It does not use folders, so your local folder structure is irrelevant for Lightroom.

If you do use Lightroom Classic, then you may have moved or copied the photos to a new location while you imported them. That will make you lose the original folder structure. You should use 'ADD' at the top center of the import dialog if you want to maintain an existing folder structure.

If you did use 'ADD' and still see all the photos in one place, then perhaps you are simply looking at the wrong place. If you select 'All Photographs' for example, then that is what you will see: all photographs, regardless of where they are stored. That is because All Photographs is not a folder, but a collection. Same for 'Previous Import', which is also a collection.

If you click on All photographs in the Catalog panel, you will see them all lumped together.

The Folders panel displays the folders.

If you can't see the Folders panel, right click the Catalog panel, and choose Folders.

Did you select to "Copy" in the Import dialog?

If you already have arranged the photos in folders at the target location, select "Add".