You will need to contact Shopify’s support team with your store URL (yourstorename.myshopify.com), stating the reason why you want to extend your trial.
In order to gain access to your Shopify store to manage the domain in question, we will need you to navigate to our Contact Us page and log in to your store. This will allow you to speak with a Shopify Support Advisor that can temporarily extend your trial for a short period of time and help transfer your domain between stores.
How is your new store coming along? I’d love to hear more about your plans and share some great resources to help you on your journey.