Microsoft Teams has not made End-to-End encryption Generally Available. Here are some good articles and FAQs if you seek to utilize it.
GA Announcement - https://techcommunity.microsoft.com/t5/microsoft-teams-blog/end-to-end-encryption-for-one-to-one-microsoft-teams-calls-now/ba-p/3037697
Preview Announcement - https://techcommunity.microsoft.com/t5/microsoft-teams-blog/use-end-to-end-encryption-for-one-to-one-microsoft-teams-calls/ba-p/2867066
Teams Security - https://docs.microsoft.com/en-us/microsoftteams/teams-security-guide#encryption-for-teams