To cover the published literature you need to search a range of key databases. Searching multiple sources allows for a comprehensive search as not all databases have the exact same coverage. These databases should be outlined in your protocol.
This page lists some health sciences databases that are commonly searched for scoping reviews. Please note that this is not an exhaustive list as the Library subscribes to over 50 health sciences databases.
Also consider searching databases outside of the health sciences that might be relevant to your topic by checking out the A-Z databases list on the Library home page.