If I were in your shoes, I would probably start by going through all your MSCF course notes, focusing on the content from the financial data science, financial computing, and stochastic calculus modules first (starting with where your memory is most hazy). You went to a top-notch program, so I would make use of the materials you amassed during your time there. Once you regain your understanding of these 3 core sequences, I would move to your ML, time series, and finance (investments, options, etc.) course notes. Alongside this I would think about what area you’re looking to apply for jobs in, and rinse and repeat all the things you did when applying for internships/jobs originally before you started to experience your health issues.
I’m glad to hear you are back on your feet. Good luck to you man—I’m sure within no time your confidence in your understanding will be back and you’ll be ready to hit the ground running.