What happens to the plates?
Off — and the DMV will not take them at a counter
Rhode Island no longer accepts canceled plates in person. Cancel online, put the plates in the Drop Box inside any DMV branch during branch hours with the Affidavit for Cancellation of Registration, or mail them by CERTIFIED MAIL to RI DMV, Attn: Plate Office, 600 New London Avenue, Cranston RI 02920. For drop box or mail, two conditions people miss: include a photocopy of the owner's photo ID or a copy of the registration, because plates returned without it WILL NOT BE CANCELED; and enclose a postage-paid self-addressed envelope, or the receipt will not be sent.
Source: Rhode Island DMV, Cancel Plates / Registration