Membership - Convert Free Memberships to Paid Memberships in One Year

Hello!

In order to populate our BuddyPress/Membership site quickly for our launch, we allowed our first 300 members to join using a Subscription choice that was free.

In one year, we need the free subscriptions to expire and properly transition members who wish to renew into a paid subscription option.

I have the free subscription (titled Founding Member) currently set to finite and one year.

What is the proper way to ensure that when their free subscription ends, that members are emailed or prompted to select another subscription method? Is it enough for them to receive the Membership communication which alerts them to renew prior to their expiration? I don't understand what will occur through the Membership plugin system when their current free subscription expires.

I'm attaching a screen shot of what a current member's Subscription details page shows them. The free membership that the member originally selected was "Founding Member" for $0. I have that subscription set to Private - does this mean that they will be unable to renew that subscription and will have to select one of the other options (which is what I DO want to happen.) I must avoid a Founding Member subscriber from renewing their free subscription.

Thanks for your help!

James