Canva and Adobe Express both have built-in tools to help you find images to use in your projects. You'll still want to cite these images to the best of your abilities based on your instructors requirements. There is a way to find that information to complete your citations.
Canva
Before you add the image, select the three little dots on the image and you can find the image details. This will tell you the creator, the site the image is from, and any licensing restrictions.
Alternatively, if all the images you selected are from Canva, and you've gotten approval from your professor, you could write the following statement: Unless otherwise stated, all images are licensed under Canva.
Adobe Express
In Express, first add the picture to your project. Once the photo has been added, select the photo and click the little i icon that appears on the right. This will then tell you then creator, website and any licensing restrictions.
You may also want to explore the Citing in Digital Assignments guide, and the Finding Free Images and Audio guide.