Lookup for FHIR R3 Extension for use in FHIR R5

Source ElementUsageTarget
Extension.idUseElementSameNameExtension.id
Extension.extensionUseElementSameNameExtension.extension
Extension.urlUseElementSameNameExtension.url
Extension.value[x]UseExtensionhttp://hl7.org/fhir/3.0/StructureDefinition/extension-Extension.value