Depends what subjects and what notes they are. If there is stuff that you could use within the notes on other questions then do that. (Such as maths where you can do questions that require information from the notes.)
Grab a pack of highlighter pens and strategically colour code what you have to learn.
I don't know what I definitely need to know (if that makes sense) - like, anything could come up - so I'll need to study everything? Which seems almost impossible.
Depends what subjects and what notes they are. If there is stuff that you could use within the notes on other questions then do that. (Such as maths where you can do questions that require information from the notes.)
I'm studying Law. And I feel like it would be impossible to learn all the hundreds of pages I have. Especially when I don't know which parts are essential for the exams in those subjects
I don't know what I definitely need to know (if that makes sense) - like, anything could come up - so I'll need to study everything? Which seems almost impossible.
I had to learn 120 pages for an exam once, and what I suggested worked really well for me at least. I assigned a particular colour for a specific purpose; i.e. I chose Yellow for highlighting definitions, Orange for key concepts, Green for factual information and Pink for things I struggled to understand. I have to stress that in order for this to work effectively, you will need to read the content actively. Start with the first page and read it actively; you will begin to notice that not all of the content is key content. There are always nuggets of important information buried in details of text. The goal is to sift through this and selectively highlight (Yellow, Orange, Green, Pink depending on context as described above) the key information. If you continue this process with the rest of the pages, at the end you will realize that it will just be a matter of going through the highlighted parts for it to sink in. I use this strategy for all of my exams; I got as high as 95% in some exams by applying this technique. I personally dislike making notes; I only write notes for topics that I know absolutely nothing about and if there are no good notes available from other sources.