if you want just a simple click and go (it looks like thats just what you want)
download this on play for 6bucks
FolderSync enables easy sync of files between cloud storage and Android devices.
play.google.com
it's the sync software, if you currently use googlesync/amazon? that can do that too and sync to local files
then you just need to have a basic external drive like a
Western Digital 8TB My Book Desktop External Hard Drive, USB 3.0, External HDD with Password Protection and Backup Software - WDBBGB0080HBK-NESN
this is essentially just a hard drive in an enclosure w/ a powersupply
if you want a more portable (you can just unplug it and store it in your safe)
WD 5TB My Passport Ultra, Blue, Portable External Hard Drive, backup software with defense against ransomware, and password protection, USB-C and USB 3.1 - WDBFTM0050BBL-WESN
you don't have to install any software/drivers when you plug it in, it'll just be another drive, i mean you can install the westerndigital software, but i wouldn't
so buy an external drive
download the app, set local storage (computer external drive) and sync
you can even just download the app now and sync to the c:\drive to test it out and you can sync wifi so you don't need to plug in, just task it to execute at 3am or something