[WP Smush Pro] Downgrade your PRO plugins to free

Hi,
I have monthly all access subscription and I want to sell one of my websites whete I have your PRO plugins installed (WP Smush Pro, Hummingbird PRO, Smartcrawl PRO...). The buyer doesn\'t subscription and he doesn\'t want to buy new.
What can I do?
Is there a way to downgrade PRO plugins (WP Smush PRO etc.) to free Wordpress repository versions without losing data?
Thanks,
Jiri