Would you prefer to be confident or competent, assuming you had to choose between the two? Imagine you had to speak to a group of strangers about a topic that you know about, would you rather be confident or competent as a foundation for preparing a presentation?
I think confidence is over rated and shouldn’t be sought as a goal. Confidence will come as a consequence of being competent and meeting the goals of your presentation. Confidence will find you. You don’t have to seek it. Maybe you need to look confident rather than actually feel confident. It is unrealistic to think you will be confident when doing something for the first time. My suggestion is that you build your competence through practice and coaching and live with any unhelpful feelings until they dissipate or you get used to their presence. Focus on what you are doing during preparation and delivery instead of wanting more confidence. The confidence will come as a consequence. It will find you.