Be more specific.
When you import pictures into Lightroom you have many options.
I think that the default one is to live the pictures where they are and only insert them into the catalogue complete with the folder. If you choose to move them, Lightroom will create folders according to your specifications, the default being by date, this creates many folders that group pictures by date.
In Lightroom the folders you see in the library pane are in fact the folders where the pictures reside, in fact this pane is an exact view of your folder tree on the computer and ant change, moving, creating new ones or renaming folders, is as if you have done it in Explorer. So if you by mistake MOVED your pictures by importing them in Lightroom then there isn't an undo option as there issn't one in Explorer. If you copyed them during import then the original folders and pictures remained where they were and Lightroom created new ones that you can delete.
so depending on what you have done you may or you may not undo it.
I strongly suggest that you watch the many tutorials in the Internet which are wery good in using Lightroom , when you ger the hang of it, and it's not hard, you'll find that this is an extremely powerful program and pretty easy to use
Hope that helps
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera