Transfer images from posts to media library

Hi,

Ive updated my blog with new look and I had to export/import all posts,images and etc. In the new version when user is browsing the categories, posts appear as list and in left they have preview image. The images are taken from media library of posts,however during transfer some of the images didnt went into library directly – they are appearing inside the post but they are not in the library which lead to missing image in the preview. My question is – can you recommend me easy way to put all images from posts into media library – plugin or something else,otherwise Ive to do this by hand and its a lot of work, it will take forever because Ive few thousand articles.

Thank you