Did you bother to look in the app store for the app? It's in your hand and with a few clicks and wee bit of typing you can answer your own question.

Does Last Pass work with Firefox on iPhone

If you are referring to the LastPass extension then it will not install on Firefox for iOS/iPadOS as Firefox is basically a wrapper shell for webkit due to Apple's restrictions on what browser engine can be used. Though maybe in future in the EU as Apple is or will be allowing other browser engines in that market. https://support.mozilla.org/en-US/kb/add-ons-firefox-ios

The LastPass extension is for desktop Firefox on Windows, macOS, Linux.

/moved thread from Firefox to Firefox for iOS section.