Upgrading from OS X 10.6.8 to Mavericks: needs

I need to upgrade my operating system, which means I need to upgrade parallels.
I'm hoping people can help me figure out what I need.
My Mac is running 10.6.8. It has parallels 6 installed, and Windows XP in it.
I want to upgrade to 10.9 Mavericks. I think I need Parallels 10. But how do I get there?
do I upgrade my Windows OS first? If so, which Windows?
do I then upgrade Parallels?
and then up grade my mac OS?

I was thinking of upgrading to Windows Vista because then I wouldn't ahve to do any complicated data migration. But it looks like Parallels 10 doesn't support Vista. I'm not sure how I'd perform the data migration--I do have external hard drives, just don't know how to format them and link them to Parallels.

Do Windows Vista, 7, and 8 all work with Parallels 6?

And when I get my Windows OS upgraded, do I then upgrade parallels? Will 10 work on Mac 10.6.8? Is that an easy upgrade or will there have to be extensive reinstalls?

thanks for your help.