When I am in the Develop tab I have been selecting "remove" instead of "delete from disk" when there is a photo I don't want to use. I know that "remove" only takes the photo out of the film strip but now I would like to permanently delete many photos I originally removed. How do I find those. Are they all just mixed in with the photos I edited or do they go to a specific location?
They remain exactly where they originally resided in your Operating System structure. They have just been removed from the Lightroom Catalog. If you wish to delete them from your system folder structure then you need to do that from within your Operating System.
Remember that your images are not "in" Lightroom. Your images are imported into folders on your hard drive and are added to the catalog. The catalog is a database that keeps track of the images that you choose to keep track of as well as the adjustments you make those images. When you choose to "remove" an image, that just removes it from the catalog. The catalog stops keeping track of that image. But the image is still in the folder along with all of the other images that were imported.