If you sort by most recent first on your Kindle they should be on the 1st page and "new".
Did you download the ebooks from Amazon via K4PC (rather than targeting your K3)? If so, you need to strip DRM before they will work on your K3. See Apprentice Alf's Blog for more on DRM. A simple test is to try to view a MOBI using Calibre's built in viewer, which will work if it is DRM free.