Firefox can't directly import IE Favorites, you need to export in HTML format and then import that file into Firefox.

In IE:
File > Import/Export - Export to HTML file

then in Firefox:
Bookmarks > Organize Bookmarks -> Import & Backup - Import HTML... = From HTML file

Well.. I tried it but no dice.

I clicked E: (for USB memory stick) I saw the Yellow-Star denoting Favorites, among files on USB stick

Then I clicked "File"( at upper left, on toolbar which displayed) But saw nothing which stated "Import/Export"

You need to do the export from Internet Explorer on the PC where those Favorites came from.

Well, how does it get from one computer to the other?

Thru the air? There has to be some medium.

USB stick, CDR, or whatever media the bookmarks.html will fit on.