cgaliher is right just a small "correction
get-moverequest -targetdatabase "Mailbox database 1499571873" | fl ExchangeGuid
It should return something like
ExchangeGuid : 0c4a031c-2ff5-4b4f-920a-ceeb811be877
ExchangeGuid : 0c4a031c-2f55-4b4f-920a-ceeb812be877
remove-moverequest 0c4a031c-2ff5-4b4f-920a-ceeb811be877
remove-moverequest 0c4a031c-2f55-4b4f-920a-ceeb812be877