How to inherit a field to sales order from leads?

hello

i want to add a product field in the sales order form. And i have added it successfully.Similarly i have added a product option in leads and opportunities too. When i enter a new lead i can enter the product for the new lead.And when the lead is converted to opportunity the name of the product appears automatically on the opportunity of the converted lead.the i converted the opportunity to quote but the product name does not appears in the sales order form automatically...

Can anyone please help to resolve my problem....
i will be very greatfull for the help........

pleaseeeeeeeeeeeeee