I think this is not possible because when we submit to a journal we have to confirm that the article has not been published elsewhere and is not under submission.
If it was published only in the CONFERENCE PROCEEDINGS, I think you can do more update on it and forward for publication in any journal of your choice.
In my opinion, if a conference article is published as an abstract or extended abstract; it can be published as full text paper in any journal. However, if one publishes a conference paper as lead paper or research paper, that must not be duplicated. Better improve the manuscript if its a review paper with thorough revision, re-analyse and update the information, remove plagiarism and then only present the review article, but not any research article.
I agree with Mr Ranjan if the conference paper is only published as an abstract. When we submit a journal paper, we have to confirm the paper has not been published elsewhere. But you can use 10 - 30 % for an extended version.