You probably just need to clean the bearing which is in the middle of the wheel. If you take the tire off and then brush it with some bearing cleaner or WD-40 it should solve the problem. Usually, it’s just some debris that is in the wheel bearing that causes that squeaky noise. If you have a scooter with a disk brake system (not electromagnetic) then you may have to loosen the brakes so the pad is not rubbing the disc.

Here is a video that can help with your Mobility Scooter maintenance: