Dash cams record on loops and you can usually change the video lengths. Mine has a button you can easily press to mark that video (and the one before/after if less than 1 minute in/to go) which moves that video to a different folder and prevents it being overwritten. It also does that automatically if it senses a crash. If you have a large enough SD card you won’t have to transfer it anywhere for quite a while depending on how much you want to save. I go a few months of saving the odd thing before moving them over to my laptop

Is it possible just to copy your files on your laptop\desktop to the opencloud folder once it’s setup and wait for them to sync? It might take a while but would be the easiest, plus giving you a backup copy on your hardware.