Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello,
E5 is a commercial product and Family plan is a consumer product. Microsoft's commercial and consumer products are from two separate ecosystems, this is why you won't be able to simply switch over or find it in Admin Center.
You will need to cancel your E5 license first in Admin Center > Billing > Your products
Then go sign up for the family plan here: https://www.microsoft.com/en-us/microsoft-365/try-copilot/individuals
Please know that you need to have a separate personal Microsoft account to sign up for the family plan. If you don't have one yet, you can sign up via https://account.microsoft.com.