YOu can reinstall the Scrivener software from the DMG file.
The only thing is any custom templates or some preferences. YOu can go to your old machine and Save your preferences as a file then on the new machine you can load those preferences or just reset your new preferences either way.
Your actual work are your Project File(s). Simply copy them to your thumb drive then copy them to your new computer.
Well What I did was go to your desktop and create a folder. I named mine Scrivener.
Then inside that folder create another Folder and name it PROJECTS.
Then put your Scrivener Application in the Scrivener folder.
Put your projects in the project folder (inside the scrivener folder).
THen you can put your SCRIVENER folder wherever you like and it contains the application as well as all your documents. That way you can always copy this whole folder to another hard drive or a thumb drive as a quick backup.
I put my SCRIVENER FOLDER inside my applications folder. Anytime I save a new project I simply go to APPLICATION > SCRIVENER > PROJECTS and there is all my SCR projects I have worked on.