Search for a folder named bookmarkbackups. It should contain files whose names contain dates, so you can identify the most recent ones.

By default, Windows hides all of your Firefox data. In order to track it down you may need to turn off that feature. This article has the steps for Windows 7, which I think are applicable to the desktop side of Windows 8.1. http://windows.microsoft.com/en-us/windows/show-hidden-files

Actually, this may be easier...

If you have the old drive connected as, say, drive E, go to:

E:\Users\username

Then click in the address bar and paste this after that and press Enter to open it:

\AppData\Roaming\Mozilla\Firefox\Profiles

Normally you only have one folder there, which has a partially random string of characters followed by "default". In that case, click into that folder and look for the bookmarkbackups subfolder.

If you find multiple profile folders, look inside to find the most recently updated backups.

To restore the backup files, see: Restore bookmarks from backup or move them to another computer

Thank you for the help. I was able to use the menu button solution offered in the Fire Fox knowledge base. I made it simpler. I used the menu to pull up the existing profile folder:

click on menu click on help menu (the question mark icon) Click on troubleshooting information click on show folder

This opens the profile folder in windows explorer.

Then in the menu click on the exit icon to exit Fire Fox.

Then I opened the old drive in another windows explorer window.

clicked on the program files folder.

then searched for .json files.

This brought up the files in the Fire Fox profile folder.

I copied pasted the latest bookmarks over to the new install or Fire Fox profile folder.

Then under bookmarks loaded it from there under:

show all bookmarks/import backup/restore

Click on the file I added.

Since it was a new install there were no other bookmarks to overwrite.

Then went into windows explorer and set it so I could see hidden files and folders. That also makes life easier!

Thank you again for your help!