You will have to take it to an automotive shop.
Since There Is No Transmission Dip Stick On My 2005 Chrysler 300 How Do I Check My Transmission Fluid?
This doesnt really help but I was told by a mechanic that you can buy a transmission dip stick for the car for like $100. I havent done it yet but I'm sure you can buy it ffrom the chrysler dealership. If I find a site that sells one I will post it here.