Hi @nic.wei66,
Thanks for reaching out. No, it is not required to purchase the Stripe Marketplace Express plugin.
The Marketo template is already using the default Stripe plugin developed by Bubble, and all the logic is already implemented for you. The only thing you need to do is simply configure the plugin with your own API keys and feel free to test the payments on preview!
Here you can find the Marketo docs. It has a table of contents that will guide you through the whole template information about pages, data types, reusable elements, etc., but the most important sections are Setup Guide and Things to Note - to setup the payments, all the plugins, check admin rights guidance and others.
Best,
Alex