Catalog issue

Please can someone help me sort out a catalog issue I have?

I have come back to using Lightroom after a number of years, my catalog is arranged by years and all files are stored on a dedicated hard drive, backed up to a NAS, labelled "Lightroom".

All files are stored in Lightroom (D:)\users\Lightroom\Pictures

My files are somehow split into two file structures in the folders pane but both structures point to the same file location on 😧 (See screenshot)

I have in the past tried to correct this and got into a terible mess so would appreciiate any help to enable me to get this all into one list as my OCD is going into overdrive!

Thanks