To find your archived forms, simply click on the 'bin' icon on your registration dashboard.
However, if you'd archived the forms using the 'archive' feature on your 'Registration dashboard', you cannot retrieve the forms as this would archive the forms permanently. They will only be available as read-only versions for your records.
But, if you deactivate a child from your 'children's register', the system will auto-archive the child's forms. This is 'temporary archiving' and the forms will be automatically 'unarchived' if you choose to 'activate' the child later.