The judge must examine all persons appearing before him pursuant to this chapter, each separately, and any report of the investigation provided pursuant to the last section and if satisfied that the interests of the child will be promoted by the adoption, he must in the adoption of all foreign born persons make a finding of facts as to the true or probable date and place of birth of the foreign born child to be adopted and make an order declaring that the child shall thenceforth be regarded and treated in all respects as the child of the person adopting.