It sounds like you are a customer receiving a package you bought from a seller that uses Square to process their credit card sales.  If that is the case you would contact the seller you purchased the item from and they can either arrange for the item to be resent or can arrange a refund.  If that fails you can then file a dispute with your credit card company, but you should first try contacting via email or phone the business you purchased from.

Square is just the credit card processing company and not the vendor/retailer, and this is a support forum for those that use Square as a credit card processor.