| | on his students' notes/in
John is a student studying mathematics at university. Every week before the lecture, the lecturer will upload a PowerPoint file onto the online system accessible only to students enrolled in the course. The PowerPoint files will contain the important things the lecturer is going to talk about in the lecture. On/in those slides, students will find point forms or complete paragraphs. Is it correct to say
-On John's students' notes, he will find all the important information he needs to write the mid-term essay.
ON sounds wrong to me and IN should be used. Do native speakers agree?