@RadhikaMendhe-8136 - I am able to get the list of apps using below API endpoint with mentioned permissions in the documentation.
https://graph.microsoft.com/v1.0/appCatalogs/teamsApps?$filter=distributionMethod eq 'organization'
Could you please add the required permissions & try it again.
If you are using postman, please generate a access token with required permission and use it while sending the request.
Also please use delegated permission because application level permission is not supported.
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