@QuynhNhuPham ,
@Chris_Hofer is correct, there are no plans currently available for individual users or smaller organizations that may benefit from that. To get access to a paid account or instance, you need to request a demo on Instructure's website, you'll schedule a time for a call and a live walkthrough that will allow you to check out everything on Canvas in action, and from there you will discuss pricing based off of your school, school district or other organization / business's needs.
Free for Teacher and K12 Free for Teacher accounts do not provide you with access to an admin account. The only admins of that instance are employees of Instructure that manage it.
I hope this helps as well! If you are interested in requesting a demo for your school or other organization, feel free to check this out here: https://www.instructure.com/request-demo
All the best!