Hi NJHitmen, and welcome to the forum.
If your projects are already set up on the iPad to sync to your Dropbox account, then accessing those projects on the Mac is fairly straightforward.
We have this Knowledge Base article on syncing via Dropbox, and it includes our recommended workflow.
You’ll need to first install the Dropbox desktop client on the Mac, which will add a Dropbox drive to your Mac’s Finder sidebar. On the newer macOS, that’s typically in the Locations part of the Finder sidebar.
You can use it to access the Dropbox storage from within Finder. This is the typical Mac navigation process of double-clicking on each folder until you see the .scriv projects in the Finder panel.
Double-clicking on the .scriv project that you’d like to work with should have your Mac open that project in Scrivener.
If you’d like to make accessing these projects easier in the future, you can use Scrivener’s File > Add Project to Favorites to create a list of your favorite projects. Then, accessing them will be through File > Favorite Projects in Scrivener.
Something to keep in mind is that Scrivener will back up your project on the Mac each time you close it at the end of a writing session. And, I recommend closing it on the Mac before switching to the iPad.
Syncing also isn’t instantaneous. Nor is it automatic. You’ll want to keep tabs on the Mac’s Dropbox icon in its menu bar to make sure Dropbox has finished syncing before switching to the iPad.
And on the iPad, you’ll want to tap the circular arrows to ensure everything is synced before working and when you’re done.
By the way, Apple do not permit apps on their mobile devices to interact with the data in another app. That restriction prevents us from having the Scrivener app automatically back up the user’s information to the Files.app or Dropbox.app.
We have this Knowledge Base article that explains how to create manual iOS backups.
I recommend adding that manual backup process to your writing habits when working with Scrivener on a mobile device. That way, you’ll have additional levels of protection for your work.