Backup a portable drive not connected to computer

I have been tirelessly converting 40 years of movies,vhs, and digital tapes of my family to digital files and storing them on a portable drive. I want to create redundant files to ensure their longevity, which means a lot of data. I currently have Carbonite for my computer, but I don’t want to leave them there taking up needed space. Any ideas for an online storage for free that will not erase my files over time?