I believe either the car lane or bike lane, but not on sidewalks or recreational bike paths. That's based on the actual law here: https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXIV/Chapter90/Section1E

Plus this page from the Salem PD has some notes: https://www.salemma.gov/salem-police-department/awareness/pages/scooter-law

Though this ultimately depends on the type of scooter I believe. Slower scooters can likely get away with bike path riding for example (I see it all the time, no one cares if you're going <20 mph and slowing down for pedestrians and slower cyclists). Don't go flying 30 mph in a bike lane either, if you can reach those speeds you probably belong in the right most travel lane.