Not able to post a JSON object to ASP.NET WebAPI

I need to pass the following JSON object to my ASP.NET Core 3.1 Web API... how can I access this object from the API?

{
    "client": {
        "clientID": "3529",
        "clientData": "This a test data"
    },
    "selectedUserIDs": [
        3549,
        3567,
        3546,
        3561,
        3532       
    ],
    "selectedDepartmentsIDs": [
        10695,
        71,
        72,
        121     
       
    ]
}

Here is my API controller

[HttpPost("/api/client/{id}/savedata")]
public ActionResult SaveClientDetails(int workflowID, [FromBody] Clientdata data)
{            
    //save operation        
}

and my various classes:

public class clientdata
{
    public client client{ get; set; }
    public List<selectedUserIDs> selectedUserIDs{ get; set; }
    public List<selectedDepartmentsIDs> selectedDepartmentsIDs { get; set; }
}

public class client 
{
    public string clientID { get; set; }
    public string clientData { get; set; }
}

public class selectedUserIDs
{        
    public int Ids{ get; set; }
}

public class selectedDepartmentsIDs
{        
    public int Ids{ get; set; }
}

I am not able to access this complex object in my Web API body. In Postman, I'm seeing the following error:

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "|10eabbbb-4a15387d9152b7d6.",
    "errors": {
        "$.selectedUserIDs[0]": [
            "The JSON value could not be converted to System.Collections.Generic.List`1[ClientCoreAPI.Client.Entity.selectedUserIDs]. Path: $.selectedUserIDs[0] | LineNumber: 6 | BytePositionInLine: 12."
        ]
    }
}