Check you email to see if you received an automated email invoice from firstname.lastname@example.org. Be sure to check your spam and add this email to your contact list to ensure you receive all future automated emails such as password resets, invoices, etc.
Additionally, all your invoices are stored on your 'Invoices' page for easy access. Simply log into your account, select your avatar (near top right corner) and select 'Invoices' to see a list of your past charges. You can view or print your invoice by selecting 'PDF'.