Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
The process to switch from the Microsoft Family subscription is provided on the link below.
Basically you need to disable the recurring billing on your current subscription by going to your account on this link (https://account.microsoft.com/services/) click Manage on the subscription and from there you can disable that.
Then, when your subscription expires, you then need to take out a new subscription to Microsoft 365 Personal:
https://www.microsoft.com/en-ie/microsoft-365/p/microsoft-365-personal/cfq7ttc0k5bf
Provided you use the exact same Microsoft 365 account for the new subscription, you will still have access to all your files and the same 1TB of OneDrive storage.