ok, there's your problem :)
firefox is for messing around on the internet
you need to mess around on your computer
let me think how we can do this
open firefox, your used to this
go to the menu that says bookmarks and see if there's something there labeled "manage bookmarks"
if you find it, click it, an window will open, look for a menu at the top that says "import bookmarks"
that's what you want to do, import the bookmarks from your old hardrive
if you get this far let me know and I'll try to walk you through the next steps, it's not hard
what version of windows are you using, stuff looks different on different versions
edit for clarity: ther are two ways to do this, let's try this first