What snet should i get ihn the shampoo i am getting for my guinea pig?

Something made especially for small animals. They sell it at petsmart.com . If not guinea pig shampoo, you could use ferret shampoo. Just be sure that it isnt anything made for cats, dogs or people. It can contain chemicals, or be to strong for a guinea pigs skin. They have very sensitive skin so that's the thing you have to watch out for.