Hi
@vanzadelhoff and welcome to the forums.
Basically the way you relocate any file, movie or image using Lightroom is to drag them from one folder to different folder. In your case that target folder would be on your external hard drive.
Before you begin quit Lightroom and make a catalog backup. AND make a
full system backup (Time Machine would be ideal) of all your images and the Lightroom catalog.
The first question I have is are all your movies under a single folder or they scattered across multiple folders? From you question it sounds like the latter. That being the case then I suggest that your first step is to gather them all together in one folder on your current internal hard drive.
So in Grid view make sure the left panel is open and click the "+" (Plus) pull down menu and select "Add Folder...". This will be the top level Folder to hold all your videos. Make this a separate folder from you existing top level folder that holds all your images. For example if all your images are in a folder "Lightroom Pictures", make the new folder something like "Lightroom Movies" at the same level. This will make the following process much easier.
Depending on how many videos you probably will want to add additional sub-folders maybe by year (YYYY) or month and year (YYYY-MM). The actual name structure is not critical, but it is good to establish a reasonably consistent structure so that there are not too many files on just one folder.
The next step is to begin to gather all your movies into the new location. Do this in the Grid and selecting the top level folder that contains everything in you catalog. "Lightroom Picutures" in my example above. Open the Filter bar and click "Videos" icon in the Kind box on the very right. You now will see all the videos in you catalog in the Grid and you can begin moving them to the new target folder.
If you going to organize by date then select date as the first filter criteria, make it hierarchal (pull down menu). You can now see how many video clips you have per year. If it is less than 1000 then I would just put them into the YYYY folders and not worry about splitting them into months.
Start by selecting the year or the year and month in the filter bar. That will show only those movies that match that date. Select them all (Cmd-A) and then by clicking and holding on the image (not the border) of any of the selected images and drag the resulting stack to the new folder that you previously created.
All the images should start to disappear from the Grid as they are moved. This is because your destination folder is not included in your source folder. This makes it easy to keep track of exactly what has moved and what still needs to be moved. You can then select the next chunk and move it to the new folder.
Moving between folders on the same hard drive is very fast because the files them selves are not copied. Only the hard drive indexes and the Lightroom catalog are updated.
Once you have all your movies reorganized into the new folder to be extra safe I would quit Lightroom with a new catalog backup and an new system backup to extra safe.
Use Finder or a validating copy application (ChronoSync for example) to move your collected movies to the new external hard drive.
Finally open Lightroom again and right click on "Lightroom Movies" folder and select the "Update Folder Location" option. Use that to navigate to the new location on you external hard drive. Once you have verified that the movies are all there you can then delete that folder on your internal drive.
You may ask why couldn't I just do the same but make the target folders on the new external drive. The answer is that you could but it is going to be a lot slower and susceptible to problems. Lightroom incurs a lot of overhead to move the files to a different hard drive. Basically it trudges through a copy and delete file by file. If there is any interruption, power outage, cat walking across the keyboard in the best case your filesystem and your library is left with your files split between two drives. It is safer and probably faster to do the two step process that I describe above.
In either case don't rush the reorganization process. Be especially careful with the drag and drop. Accidentally letting loose of the mouse on the wrong folder can be tedious to clean up.
-louie
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