In the wordpress, when you upload images, the image url will be the full url, say, if you want to change the stored uploads file name all the uploaded files will lost. The default path is domain/wp-content/upload, you want to change the upload to uploads, but the images urls in your post not change, all the images will gone if you do not change the image’s url. In order to fix the images’ urls, you should update your mysql.
Use the mysql commend
Run SQL query/queries on database (You should back up your database first )

UPDATE wp_posts SET post_content = replace(post_content, 'upload', 'uploads');