One of the most important things you can do in these 1-1s is to build a feedback loop for your performance and career growth. For example,
Projects - What did you do, how well did you do, what did you do well. What mistakes did you make, how do you not repeat them, etc.
Skills and traits - What skills and practices do your company/team value. Which of them you need to level up on, what does that look like, what specific things should you do to level up. Which of them you're doing a good job on, how can you leverage this more in your position.
Career growth - What is the next level in your career, what are the responsibilities that come with it? How can you start being responsible for those things right now. You need to work according to the job that you want.
Team/company - How can you help your team become better? What are the things your manager is trying to focus on and how can you help? What recent developments should affect how you work?
There will be more things based on your role, your company, your manager that you can talk about. Remember to take notes and do a retrospective in the next 1-1.