firebase.dart

// https://pub.dev/packages/file_picker
import 'package:file_picker/file_picker.dart';

getMultipalFiles() async {
  FilePickerResult? result = await FilePicker.platform.pickFiles(allowMultiple: true);
  List<File> files = [];
  
  if (result != null) {
     files = result.paths.map((path) => File(path)).toList();
  }  else {
  // User canceled the picker
  } 

  List<String> downloadUrls= [];

  for var img in files{
    var url = await _uploadFile(img,"folder path");
    downloadUrls.add(url);
  }
}


Future<String> _uploadFile(File file,String folderName) async {

    final ref =
        FirebaseStorage.instance.ref().child(folderName).child(file);
    UploadTask uploadTask = ref.putFile(file);
    
    TaskSnapshot taskSnapshot = await uploadTask.whenComplete(() => {});
    String videoUrl = await taskSnapshot.ref.getDownloadURL();
    return videoUrl;
  }