Open PowerShell, and install the PowerShell Teams module:

Install-Module -Name MicrosoftTeams -Force -AllowClobber

Connect to the Microsoft Teams service:

Connect-MicrosoftTeams

List all users and their assigned numbers. Export to CSV if needed:

Get-CsOnlineUser | select DisplayName, UserPrincipalName, LineUri | Export-Csv -Path TeamsNumbers.csv