Yup, they weren't copied, so you'll have to plug the old hard drive back in and find them on that first and copy it. Since the files are hidden you have to type the path (drive letter):\Users\username\AppData manually, or show hidden folders to navigate the normal way
support.microsoft.com
Then copy the Firefox folder.
If you still have issues we might need to find a better way to communicate haha
Show hidden files - Microsoft Support
Learn how to display hidden files, folders, and drives.
If you still have issues we might need to find a better way to communicate haha