Can anyone tell me if Adobe Express includes free stock photos? If yes, how do I get to them?

When you're creating your project you can choose photos, design assets even logos fro mthe menu on the left. Here i have Backgrounds open and you can use any of them in your project.

Items marked with a crown icon are Stock items that require a subscription to the Creative Cloud, so in that sense are paid Stock items. Any others you cna use freely.

Edit: it's just occurred to me you might also mean using Stock from stock.adobe.com. Whilst the assets in Express all come from Stock, you won't find everything there. To use an asset from the larger Stock website you would need to have it in one of your Libraries or have downloaded it, so that you can upload it to Express and use it. Again, there are lots of paid assets in Stock, but you can also search free items by using the dropdown menu. That's my second screenshot 🙂