I have a project in sails with nodejs version 0.12.7 I would like to update my project to node 7.0.0
You shouldn't have to upgrade your project. You just need to upgrade Node. Here's a tutorial on how to install a new version of Node alongside the old version, so that if anything doesn't work with the new one, you can switch to the old one.
I'd suggest copying the project to some other place, cleaning node_modules and doing npm install to see how it works.
You may get problems with new versions of npm modules if their API changed so you may need to specify exact versions of modules that are known to work in your package.json.