Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
To move from the Microsoft 365 Family subscription to the Personal version is switching to a version with fewer features, the process is explained on the link below, basically you need to cancel the Microsoft 365 Family subscription, you should get a pro-rata refund, then take out a new subscription to the Microsoft 365 Personal version.
Steps to cancel the Family subscription:
You can check your eligibility to a refund using the steps on this link.