question

@SreekanthReddy-4938 Thanks for posting in our Q&A. From your description, did you mean that you want to install extensions on Firefox using intune? If there is anything misunderstanding, please correct me.

Firefox is a third-party browser. It is needed to ingest the Firefox's ADMX-file first and then configure extensions. It is suggested to try the following actions:
1.Firstly, please try to create a configuration Profile for firefox.admx. Please refer to the steps under "Initial setup" in the following link:
https://support.mozilla.org/en-US/kb/managing-firefox-intune
Note: Non-Microsoft link, just for the reference.
2.Then refer to the following blog to install extensions.
https://securitygeneralist.blogspot.com/2019/08/auto-installing-extensions-on-firefox.html
Note: Non-Microsoft link, just for the reference.

Hope it will give you some ideas.

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