Internet Explorer uses individual files for each of its favorites, but Firefox uses one file to store all of the bookmarks. This file is called places.sqlite inside the profile folder, and that file also contains the browsing history. For details of how to find the profile folder see https://support.mozilla.com/kb/Profiles
It is not possible to add shortcuts to the Firefox bookmarks just by copying the shortcuts to a folder.
Are the shortcuts .url files? If they are the only way I can think of doing this is to copy them to the Internet Explorer favorites folder (to find the IE favorites folder, in the Taskbar click on Start, choose Run, then type in favorites and press enter). You can then then import the favorites into Firefox, though this will import all IE favorites not just those from the USB - https://support.mozilla.com/kb/Importing+favorites+and+other+data+from+Internet+Explorer
I backed up all of my files and replaced the hrd drive. The only files I cannot find are the 1000 bookmarks that I had. IE has all of the 3 favorites I had. Even Netscape had them What is wrong with firefox that I have now lost all of those book m,arks many were new. Many were new I've been doing allot of researsh but I will no longer be using Firefox unless I can get my book marks restored. Really Really!!! Not Happy