Hi sophieestevez09 welcome to the forum
Be careful about what you use. Finding something on the web does not necessarily mean it’s free for everyone. A good thing to do is to have explicit written permission from the source when in doubt.
Here are a few topics that have discussed sources of images that you may find helpful.
Can I download images from Facebook?
https://www.sitepoint.com/community/t/websites-for-good-free-photos/236232
https://www.sitepoint.com/community/t/using-photos-from-other-websites/43981