Files/folders deleted in Dropbox are moved to the Deleted files area. Click on ‘Show Deleted Files’ option in the right sidebar. Select the files/folders you want to recover and click on the ‘Restore’ button on the right which is visible once you have selected something. You can also choose to permanently delete the file/folder by clicking on the three-dot dropdown menu and clicking on ‘Permanently delete’.
The professional plan offers up to 180 days to restore deleted files instead of the 30 that you get in the free plan.