Where to get codecs?
You need to change the format from AVI to h.264. In the top of the export window there's a section where you get to choose formats:



It's a bit confusing, because it mixes container formats like AVI and Quicktime with codecs like h.264. If you chose AVI you are limited to a few older codecs, as you've seen.

Once you've chosen h.264 you can then chose a preset. The default Match Source - high bitrate preset is usually spot-on for YouTube, as it's a good compromise between quality and file size. It will automatically match the resolution and frame rate of your sequence, so you won't have to worry about other settings.

If your video is 4K or larger you could also consider h.265, which is designed for UHD. It's a lot slower to compress, so don't bother if you're exporting HD or lower.