Mail In cars?

[P.Suits]

I just started collecting for our 2 year old son in 2019. We generally buy him one to keep on card and another to open depending on if we find 2. If we are lucky enough to find more than 2 Camaros, Mustangs, Corvettes or Gulf cars, certain trucks etc... then we add those to a collection specifically for those cars. 
     The main reason for this post is to find out how we go about the mail in process. I have looked online and can really find very little other than people wanting to sell mail in cars. If anyone could tell me how we go about this I would really appreciate it. We have been keeping the cards from the cars he opens and would like to redeem them if possible

[loaf]

typically you need 20 cards and a receipt for 20 cars or 20 dollars worth of cars in single blisters, or 5 or 9 or 20 pack UPCs...depends on the mail-in and what the retailer wants. There'll be an article a week or two before the launch of a mail-in which lets you know what you need and which retailer. The good thing about keeping the cards like you've been doing is that you won't need to open all 20 once the promotion begins because you've already got a head start. the receipt doesn't have to match the cards, just has to be from the retailer during the promotion period, which is usually like a month. 

[SAMACE26]

Yeah that is how the mail-in cars work you have to go to this certain retailer that is doing it and buy 20 hotwheels cars and bring them home open them up and send in to Mattel your 20 blister cards and the cash register receipt and a $4.99 check or money order and than with in a few weeks you get a free car in the mail. ?

Edited January 26, 2020 by SAMACE26