Have you deleted the photo files themselves or simply deleted the editing by removing the file references from the LR catalog? If the former, did you specifically make copies of the Raw photo files as backups? LR does not do this, you have to do it. When you do a backup as you are exiting LR, all that is backed up is the *.lrcat catalog file. But if you do have backup copies of the Raws, simply copy and paste them to the same location where the originals were.
If you mean that the originals still exist on your hard drive, but have been removed from the catalog, open the backup catalog in LR ( File>Open Catalog), select the photos in question and do File>Export as Catalog, placing the exported catalog on your desktop. Relaunch LR with your working catalog and do File/Import from Catalog to import the catalog on your desktop and the catalog entries will be restored.
Finally, if the Raw files were not actually backed up and have been deleted, they are gone. (Have you checked Recycle/Trash?) There is software available that will allow you to extract the small jpg preview LR made for its own use, but that is the best you can do.
Find the backup of these accidentally deleted photos, and then place these backups in the exact folders where the originals were before you accidentally deleted them.