✅ convert synchronous code to async?

//Controller class
    public string BindOrgUsers()
        {
            string result = string.Empty;
            try
            {
                FilterModel fm = new FilterModel();
                result = fm.GetUsers(Utility.GetOrgId(), Utility.GetUserId());
            }
            catch (Exception ex) { _logger.Error(ex); }
            return result;
        }

//FilterModel class
 public string GetOrgUsers(int orgId, int userId)
        {
            string result = string.Empty;
            try
            {
                string cacheKey = $"Users_{orgId}_{userId}";
                result = CacheManager.GetOrAdd(cacheKey, () => GetUsersFromDB(orgId, userId));
            }
            catch (Exception ex) { _logger.Error(ex); }
            return result;
        }

 public string GetOrgUsersFromDB(int orgId, int UserId)
{
 string json = string.Empty;
  DataTable dtUsers = Utility.ExecuteSqlDatatable("sp_getOrgNetwork", CommandType.StoredProcedure, paraUserReport.ToArray());
                    json = JsonConvert.SerializeObject(dtUsers);
}