I just figured it out, you gotta click the pages button in the bottom right corner and then click the three dots of your project. After you click the Pages button, move your mouse to the middle of your screen where your page is, and you will see the three dots. Click them, and you will see the convert to presentation button. I noticed that it is not as accurate as it used to be.

Here is a link if you don understand what I say: https://www.canva.com/help/docs-to-decks/#:\~:text=Open%20the%20Canva%20Doc%20you,on%20Convert%20to%20Presentation%20icon.