In the Transfer request  Body , The PartIdType will be “ALIAS” 

and the partyId with  be the Actual Code, Will use “000000” as below 

the Alias is the Marchart code Example a MoMo Pay Code 

{
  "amount": "<string>",
  "currency": "<string>",
  "externalId": "<string>",
  "payee": {
    "partyIdType": "ALIAS",
    "partyId": "00000000"
  },
  "payerMessage": "<string>",
  "payeeNote": "<string>"
}