They will be in the postmeta table. post_id == your post ID and meta_key == the field name.
If you don’t find the updated data then the import could be a draft post. In this case the data could be attached to a different post ID and this post ID will be a child post of the real post ID. You can look for this by looking for posts where the post_parent is the real post ID.
The errors tell me that it is trying to update a post that does not exist, but I have no idea why it would be doing that.
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