A good place to store you ALLSAFE wallet.dat files is in an online storage.
It is safer than on a USB drive as you might lose the USB drive or it fails and becomes unreadable.

Please note, NEVER only just copy your ALLSAFE wallet.dat file in an online storage place.
A rogue network administrator can just copy your ALLSAFE wallet.dat file and steal your precious ALLSAFE coins.

Best to rename and then Encrypt the ALLSAFE wallet.dat file and then store it on an online storage place.
You can use 7-Zip to Encrypt the file with AES-256 bit Encryption (Freeware).

So in short:
1. Make sure to Encrypt your ALLSAFE wallet and directly make a backup of your ALLSAFE wallet.dat file
2. Rename the ALLSAFE wallet.dat file to for example inventory.doc
3. Encrypt the file with 7-Zip
4. Move the file to your online storage