The title and body of your post seem to be asking different questions (title is about tags, body is about metadata or content). To answer the the post title, Auto Note Mover community plugin can move based on tags or note names. If “kindle-sync” is in the tags field, this will work.
If the notes are all named in a distinctive way, or you can change a setting to make them that way, you could use the Auto Note Mover plugin. If not, but they’re already in a folder (but the wrong one) by themselves, you might still be able use it.
Where are they now? Mixed in with other files in the root of your vault?
Does your import method give you any way to control where the files go, so you don’t have to move them afterward?