Yes, MoodleCloud is different. You cannot install plugins in MoodleCloud.
If you really want to try the Canvas plugin, you could install a local (sandbox) Moodle, import the Canvas questions, export them a Moodle XML, then import the questions into your MoodleCloud.
I gave this presentation last year at MoodleMoot. It might help.
MoodleMoot2019 (Global and Mountain), "How to Install a “Sandbox” Moodle on Your Windows PC/Mac"