download origin to the new computer then log in to your origin account from the desktop with your email and password you use for the account go to the my games tab right click the game icon -download for your store purchase on the sims 3 site log into there go to my store account-purchase history and download then install your store items, sets worlds, hair etc
you can also copy your saved sims folder and saved games over to the new computer too copy and paste the files to a flash drive or thumb drive then copy and paste to the new sims3 folders
