Can't copy files from USB drive to NAS

I have discovered a portable drive where I have a lot of images I thought was lost. I can open, view images and play videoclips, but when I try to copy them to my backup raid station(network) I just get an error message.

Message is translated to ny native Norwegian, so I translate it back again: System cant find the given path.(3)
I tried coying an another drives files, thats no problem.
I can also copy the files to my local drive from the USB. But even I cant copy from my local drive to the network raid. I'm not getting this. Ah, and I can see all folders and files have an atribute set-a----- I have no idea what that does.

Any tips? What Exactly is the (3) code?

Regards Trond

What happens if you do the same direct copy using File Explorer?

Unless antivirus is doing something strange, I'd suspect something to do with the file/folder names being copied which might be confusing the NAS. Maybe copying them to a local drive first sanitises them, such that copying to the NAS then works.

Either that or the NAS is returning the wrong error message for whatever the situation is. That isn't unheard of.