Dumb jffs backup/format/restore question (sorry)

[bpsmicro]

AC86U running latest Merlin, and I followed the instructions to install Skynet on it. I have a 32Gig USB key, but I used the UI to format so it's formatted as FAT.
After reading & learning more, I want to install Entware. It requires that the USB key be ext formatted, and I know now I can do that via ssh.

Is it as easy as using the UI to backup my jffs to a local .tar file, use 'fd' to reformat to ext4, the Restore from the UI to plop the contents back on, and presto? I'm thinking maybe shutting down Skynet before doing this in case there are locked files. Anything else I should know?

 

[ColinTaylor]

EDIT: I deleted my previous answer as I misread your post.

jffs is completely different from the USB device. When you format a USB device the jffs partition is unaffected. jffs is a part of the router's on-board flash memory.

 

[bpsmicro]

EDIT: I deleted my previous answer as I misread your post.

jffs is completely different from the USB device. When you format a USB device the jffs partition is unaffected. jffs is a part of the router's flash memory.

Oops! Learned something new. So in my original question, replace "jffs" with "USB", except now I need to rethink the backup strategy, probably using WinSCP to just copy away & then back. And now that I know what I'm looking for, the only thing there is the skynet folder and a myswap.swp file.
I'm not a Linux guy, but I know just enough to be dangerous.