Press Ctrl + Shift + A or go to the "3-bar" menu icon located on the far right of the Navigational Toolbar, click Add-ons, then Extensions. There you will see a list of your installed extensions.

I did that, but don't see where I can find an actual list of what I have on my computer. Are 'Extensions' what I need to look at?

sorry, yes. I should have been more clear.

You can also see some data including installed extensions in Help > Troubleshooting Information.

• https://support.mozilla.org/kb/Using+the+Troubleshooting+Information+page

• https://support.mozilla.org/kb/extensions-add-features-to-firefox
• https://support.mozilla.org/kb/customize-firefox-with-add-ons-plugins-and-extensions

It's been awhile since I had check them, and had forgotten how. Thanks!