Start a new trial: https://sqspthemes.com/squarespace
If your old site had an annual subscription, you can fill out a refund form: https://support.squarespace.com/hc/en-us/requests/new?ticket_form_id=360000070568 Depending on the amount of time left in the subscription, you may be eligible for a prorated refund.
Source:
https://sqspthemes.com/blog/change-your-squarespace-template
Top 50 Squarespace Template Shops: https://www.sqspthemes.com/blog/premium-squarespace-templates
