Simple relationship in mongodb async

I’m trying to figure our how relationship work in realm, it should be very simple, and the documentation is great I still cannot figure out how to do it.

Conversation has many messages
Message belong to Conversation

Conversation.id <> Message.conversation

export type Conversation = {
  _id: Realm.BSON.ObjectId;
  name: string;
  participants: Realm.List<string>;
  phone_number: string;
  timestamp: number;
};

export const ConversationSchema = {
  name: "Conversation",
  properties: {
    _id: "objectId",
    name: "string",
    participants: "string[]",
    phone_number: "string",
    timestamp: "double",
  },
  primaryKey: "_id",
};

export type Message = {
  _id: Realm.BSON.ObjectId;
  conversation: Conversation;
  media?: Message_media;
  message_id: string;
  recipient: string;
  statuses: Realm.List<Message_statuses>;
  text?: Message_text;
  timestamp: number;
  type: string;
};

export const MessageSchema = {
  name: "Message",
  properties: {
    _id: "objectId",
    conversation: "Conversation",
    media: "Message_media",
    message_id: "string",
    recipient: "string",
    statuses: "Message_statuses[]",
    text: "Message_text",
    timestamp: "double",
    type: "string",
  },
  primaryKey: "_id",
};

Above not working.
Unsupported comparison between type ‘link’ and type ‘string’

How do I query conversation.message.length?

const conversations = useQuery<Conversation>(
    ConversationSchema.name,
    (collection) => collection,
    [requeryFlag]
  );

conversation[0].message // does not work