As the folks over at PsychCentral say:
Many kids with anxiety don’t have the vocabulary to explain what they’re experiencing or the understanding to know they’re not alone. These books can help.
There’s a pretty good selection, take a look if you think it might help. I definitely agree that, especially with younger children, they won’t have the words to talk about feeling anxiety, or to understand what is normal nervousness versus life-altering levels of anxiety. As a parent, it can be difficult to know. Maybe, one of these books might help.
What books have you read about anxiety that you would recommend?
https://psychcentral.com/health/books-about-anxiety-for-kids-and-parents