db to sqlite3 conversion in broad sense represents import of 'any' kind of database to Sqlite and saving that in version 3 format. This should of course be possible with any SQlite tool with proper version, but if you are looking for some particular type of database for import, you should check out whether it uses unique file extension to better determine the actual database file types.
In any case, you can find plenty of guides and tutorials about database migrations all over the Internet.
Updated: August 15, 2023