@Saida Yucel Thank you for reaching out to us, As I understand you want to export Azure b2c user details from the portal during the process you are not able to get mobile number details.
In order to authentication method information from the user, came across below articles
https://www.reddit.com/r/PowerShell/comments/a9rbyz/exporting_azure_user_directory_to_csv_that/
Both the articles have different approaches to get the authentication method information for the user, I tried at my end and it helped to fetch the authentication method details.
Let me know if you have any further questions, feel free to post back.