Ok, so I searched up a bunch of help articles on the Microsoft site and the Dell site, and I found an online manual for my tablet. I finally got it to turn on by pressing and holding the power button for ten seconds and then another ten seconds. Based on my research, I'm guessing that somehow I managed to shut off the screen on my tablet without turning the tablet itself off, and that I shut it down. Because when I got it to turn back on, it was like I had shut it down, where I had to sign in and everything. Whatever the cause, I'm glad I fixed it, and I hope that if anybody else has this same problem, my question and how I fixed it will help them too.
UPDATE: If you're still having trouble, you can try scrolling through the comments; I have posted more detailed instructions in one of the comments. :)