Insert data from one table to another

I have two tables Cart(ItemID, Name, Price, Quantity, CartID, CustID) and PP( invoiceID, itemID, orderQuantity, PricePerUnit, includesID). Now i have to
Insert values(ItemID, Price, Quantity)from cart table to pp table where cart.custid= session[customerID]. But the values not getting inserted into the pp table. Not sure if the AsEnumerable syntax used here is correct.
My Code:

DataClassesDataContext context = new DataClassesDataContext();
var Carts = context.Carts;
pp newpp = new pp();

var p = Carts.AsEnumerable().Select(x => new pp()
{
itemID = x.ItemID,
PricePerUnit = Convert.ToDouble(x.Price),
orderQuantity = x.Quantity,
invoiceID = invoiceNum

});

context.pps.InsertAllOnSubmit(p);