Insert foreign key into database using dapper in c#

I Want to insert into sql table with foreign key in c# using dapper, Here is my code. When I do it this way it gives me a conversion error.

public class LoanModel
{
    public int ID { get; set; }
    public CustomerModel CustomerID { get; set; }
    public int Amount { get; set; }
    public InterestModel Interest { get; set; }
    public DateTime Date { get; set; }
}

This is the method that fills the data gridview:

List<LoanModel> Loans = new List<LoanModel>();

public void FillCustomersDataGridview()
{
    try
    {
        DataAccess.ShowLoan(SearchCustomTextBox.Text.Trim());
        dataGridView1.DataSource = Loans;
    }
    catch (Exception ERE)
    {
        MessageBox.Show($"An error occured: {ERE.Message}");
    }
}

This is the method that inserts the data into the database:

public static void GetLoan(int id, int customerID, int amount, int interest, DateTime loanDateDateTimePicker)
{
    using (IDbConnection Con = new SqlConnection(Helper.ConnectionString("DatabaseConnection")))
    {
        LoanModel Loan = new LoanModel { ID = id, CustomerID = customerID, Amount = amount, Interest = interest, Date = loanDateDateTimePicker };
        List<LoanModel> newLoan = new List<LoanModel>();
        newLoan.Add(Loan);
        Con.Execute("spGetLoan @ID, @CustomerID, @Amount, @Interest, @Date", newLoan);
    }
}