Squeaky belt

Take a look at this guide: https://www.2carpros.com/articles/how-a-serpentine-belt-works

Compare your belt to the one in the pictures. If it is cracked like that, replace it. As belts get old, they stretch a little bit. As they stretch, they crack. The cracking is a sign of how worn a belt is. Once it has cracked like the one in the guide, then it is slipping just a little bit around one or more pulleys, causing that squeaking sound. Let us know what you find.

Also, if it is more like a chirp sound, I would take an old tooth brush (or preferably, a small wire brush) and use it to clean both sides of the belt while the engine is idling (only if there is plenty of room to work with). If you are not careful, you could get hurt.