After reviewing the photos on this website. Isn't our snake a Motley Striped rather than a Standard Motley snake?
http://www.reptileallsorts.com/cornphase/index.html
No, he is a Normal Motley. Stripe is a different gene entirely. I'm not sure why the snake in that picture is labled as a "Motley Stripe", Motleys that have elongated spots on their dorsal patterns like the one pictured are usually called "Pin Stripe Motleys" or "Q-Tip Motleys". Those snakes's Genotypes are still only Motley though (with the exception of Motleys het stripe, but I don't want to confuse you too much!)
I can't see the whole dorsal pattern of your snake, but I can't see any elongated spots from the pictures shown.
One of the best things about this forum is that there's SO MUCH information, so much to learn! You'll do fine as long as you use the resources here, and it sounds so far like you are! Autumn looks like a great size for a beginner. IMO judging from the hand size scale he's probably getting a bit big for pinkies. I'd bump him up to fuzzies and hoppers soon. Do a search for the "Munson Plan" to find the successful guide that many people here have used.
I personally LOVE Motleys and think that they are a very beautiful morph. I'm confident you could have gotten a Motley equally as beautiful and cheaper and more gaurenteed than the route that you have taken, but for a beginer, it's somewhat normal to go with a pet store purchase. Heck, I think everyone here understands the "I want that cornsnake NOW!" feeling!
My second Corn Snake was a Normal Motley (who looked a LOT like your guy), and yup, in my hobby infancy I bought him from a Pet Store. He grew into this beautiful snake:
Once again good luck, and I hope to see you around the forum! Also, I think Autumn is a GREAT name!