a question about Firefox add-ons

[lazarus]

I had one that I really liked on my old computer. I have access to that hard drive via USB and a dock, but the old Firefox just locks my system up. Where do I look to see what add-ons I had?

Or if anyone knows add-ons well, it's a neat one that lets you set keyboard shortcuts for groups of text, handy for filling out forms or if you have to do a lot of repetitive typing.