Send FromForm Object between APIS C#

I want to send an Object between apis but my controller is waiting for this

 public async Task<IActionResult> Post([FromForm]UserViewModel input, CancellationToken ct = default(CancellationToken))

How can I send that model as a FromForm?

My Current call:

 var userContent = JsonConvert.SerializeObject(userRequest);
            HttpRequestMessage request = new HttpRequestMessage
            {
                Method = HttpMethod.Post,
                RequestUri = new Uri($"{_apiUrl}users"),
                Content = new StringContent(userContent, Encoding.UTF8, "application/json")
            };

            var result = await _httpClient.SendAsync(request);

My model:

public class UserViewModel
{
 public string name;
 public string lastname;
 public List<IFormFile> GalleryImages { get; set; }

}