Can't see video files on memory card
Make sure they are not stored in the Camera internal memory (if has one).
Videos are usually much bigger files. What you can try is to open the mounted memory card, switch to List view and select “Calculate sizes” in CMD + J dialog. Sort files by size and dig deeper in the biggest folders until you find the biggest files.
Or try to identify approximate average size of photos and based on that you can try to search for files in the most top folder level of the memory card by pressing CMD + F and with small plus sign button you can add “File Size” criteria with “is greater than” option and put there value you identified or just something like 20 MB.
You may find files that are big but not playable by Quicktime or any video player currently installed on your Mac which means the camera uses its own format that you may need to convert.