I would like to backup my saves because a while ago nintendoland data got reset somehow and i lost it and i dont want it to happen again unless i have a backup

There is no copy data feature I'm aware of, just move and delete. Correct me if I'm wrong!

Ya but could i plug it into pc and copy folders or something?

If you formatted your hard drive with your Wii U, your files can't be seen by computers.

What Forest_Ranger said. If you're really concerned about your save files you could invest in some kind of hardware RAID unit that would be doing low-level mirroring and provide some insurance against disk failure.

Nintendo has said the 2TB storage limit is temporary so maybe when they lift that they'll make a provision for creating backups or offline copies. I know that once I have a bunch of disc downloads I won't be looking forward to the possibility of multiple days spent re-downloading my games.