I want to upload file throw Monday.com API graphql

I want to upload file throw Monday.com API graphql. I am using dart and building Flutter App. I am stuck on uploading files (images) throw API. Can you help me, with providing codebase or anything.

Future<void> _pickImage(String imageType) async {
    html.FileUploadInputElement uploadInput = html.FileUploadInputElement();
    uploadInput.click();

    uploadInput.onChange.listen((e) {
      final files = uploadInput.files;
      if (files!.isEmpty) return;

      final file = files.first;
      final reader = html.FileReader();

      reader.readAsDataUrl(file);
      reader.onLoadEnd.listen((e) {
        setState(() {
          _images[imageType] = reader.result as String?;
        });
      });
    });
  }


  Widget _buildImageField(String label, String imageType) {
    return Column(
      children: [
        Text(label),
        SizedBox(height: 10),
        _images[imageType] != null
            ? Image.network(_images[imageType]!)
            : Text('No image selected.'),
        ElevatedButton(
          onPressed: () => _pickImage(imageType),
          child: Text('Pick Image'),
        ),
      ],
    );
  }

  final ImagePicker _picker = ImagePicker();
  
  Map<String, String?> _images = {
    'TruckFront': null,
    'TruckLeft': null,
    'TruckRight': null,
    'TruckBack': null,
    'LeftFrontTire': null,
    'RightFrontTire': null,
    'SideLeftTires': null,
    'SideRightTires': null,
    'LeftRearOutside': null,
    'LeftRearInside': null,
    'RightRearOutside': null,
    'RightRearInside': null,
    'TrailerLeft': null,
    'TrailerRight': null,
  };