Firefox profiles are stored in the application data folder. To locate your old profile(s), please refer to the steps in the Mozilla support article to navigate to your current profile folder. Then navigate to the folder that profile is located in:

• Profiles - Where Firefox stores your bookmarks, passwords and other user data

However, it sounds like your old profile may be corrupt or damaged. We recommend that you don't use the old profile, as it won't work if it is damaged. Instead, you can recover important user data to your new profile, by referring to this Mozilla article:

• Recover important data from an old profile

Let us know if you are successful or if you require further support.

If regards to your original crash that caused this whole issue, you may want to view the following articles for tips on how to prevent Firefox from crashing in the future:

• Troubleshoot Firefox crashes (closing or quitting unexpectedly)
• Avoid crashes - Tips and tricks

Do you have an "Old Firefox Data" folder on the desktop in case you have refreshed Firefox and created a new profile?

• https://support.mozilla.org/kb/reset-firefox-easily-fix-most-problems

You can recover data from such a saved profile, but be cautious to recover possibly corrupted files.

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile

Note that "Reset" creates a new default profile with a time stamp appended to identify it and tries to recover settings like bookmarks and history and passwords and history and cookies and auto-fill data from the old profile, but you lose data like installed extensions and other customizations.

• http://kb.mozillazine.org/Profile_folder_-_Firefox

The current profile folder will be moved to the "Old Firefox Data" folder on the Desktop.