trouble formatting firebase Firestore data when getting for my flutter app

I'm new to firebase and I'm trying to implement instagram like stories to my flutter app using the "story" plugin.

I am trying to call this data:

the trouble I am having is trying to find a way to get and format the data in the "file" array.

this is my current code:

pubspec.yaml:

dependencies:
  story: ^0.4.0

story models:

class StoryModel {
  final String displayName;
  final String avatarUrl;
  final String ownerId;
  final List file;

  StoryModel({this.displayName, this.avatarUrl, this.ownerId, this.file});

  factory StoryModel.fromDocument(DocumentSnapshot doc){
    return StoryModel(
      displayName: doc.data()['displayName'] ?? '',
      ownerId: doc.data()['ownerId'] ?? '',
      avatarUrl: doc.data()['avatarUrl'] ?? '',
      file: doc.data()['file'] as List,
    );
  }
}

class StoryFile {
  final String filetype;
  final String mediaUrl;
  final String postId;

  StoryFile({this.mediaUrl, this.postId, this.filetype});

  factory StoryFile.fromDocument(DocumentSnapshot doc){
    return StoryFile(
      filetype: doc.data()['filetype'],
      mediaUrl: doc.data()['mediaUrl'],
      postId: doc.data()['postId']
    );
  }
}

trouble section:

                      FutureBuilder(
                        future: storyRef.where('canView', arrayContains: currentUserModel.uid).get(),
                        builder: (context, snap) {
                          if(!snap.hasData) {
                            return Center(child: Text('error'),);
                          } else {
                            QuerySnapshot snapshot = snap.data;
                            List<StoryModel> storyPosts = snapshot.docs.map((doc) => StoryModel.fromDocument(doc)).toList();
                          return Container(
                          margin: EdgeInsets.only(top: 10),
                          height: 150,
                          child: ListView.builder(
                            itemCount: 6,
                            padding: EdgeInsets.only(left: 28),
                            scrollDirection: Axis.horizontal,
                            physics: BouncingScrollPhysics(),
                            itemBuilder: (context, index) {
                              return Row(
                                children: [
                                  Column(children: [
                                    GestureDetector(
                                      child: Container(
                                        height: 100,
                                        width: 100,
                                        margin:
                                        EdgeInsets.only(right: 20),
                                        decoration: BoxDecoration(
                                            border: Border.all(
                                                color: Colors.blue,
                                                width: 3),
                                            shape: BoxShape.circle,
                                            color: Colors.grey
                                            )
                                      ),
                                      onTap: () {
                                        print('Navigate to story View');
                                      },
                                    ),
                                    Padding(
                                      padding: EdgeInsets.only(
                                          top: 5, right: 22),
                                      child: Text(
                                        'insert name',
                                        style: GoogleFonts.lato(
                                            color: Colors.blue[800],
                                            fontSize: 20,
                                            fontWeight: FontWeight.w700
                                        ),
                                      ),
                                    )
                                  ]),
                                ],
                              );
                            },
                          ),
                        );}
                        }
                      )

This code works fine getting the "StoryModel" data but I still need a way to get the "StoryFile" data from each individual "file" from Firestore and I can't figure out a code that works in the way I want it to.

so I need a way to get a List of "StoryFile" from each individual document preferably in the .fromdocument method as part of the "StoryModel" class if possible.