Connect your drives to the machine on which your catalog is present
Just copy the catalog and paste that to 3 different drives.
Generally the location of Lightroom catalog is C:\Users\UserName\Pictures\Lightroom (Windows) and User\Pictures|lightroom (MAC)
If I copy and paste, will that take a long time? Is that the only way to copy catalogs to different hard drives?
That should not take a long time.
As catalog never contain images, it is just the editing part you do.
Lightroom never store images.
Yes this is the only way that I can think of.
Thank you so much!!!
Just so you are clear, the LR Catalog does not contain your pictures, just a pointer to them plus whatever work you have done on those pictures. Thus it is a relatively small file that is easily copied, or more easily backed up automatically, preferably to a different disk using LR's backup option. The file with your pictures can be huge depending on the number and size of each, but those also need to be backed up to a different disk. LR does not address this, so hopefully you have some tother backup system.