@brian1945 : extensions are available in Firefox on Windows, macOS, Linux and Android
If you mean iPad and iPhone devices, then Apple requires all browsers there to use their own engine (WebKit) that powers Safari, and they haven't allowed extensions. The EU has recently forced them to allow this, but unless Firefox decide to go to the effort of making a browser that can only be used on iPhones and iPads in that area, then no.
Switching to an Android phone or tablet will allow you to use extensions on the go.
Otherwise, in the desktop version of Firefox, go to Menu -> Extensions and Themes and use the search box at the top to find one you want
