Since you seem to be new to pet battles, be sure to see this guide to help you start:
Guide: Your early pet roster - Gameplay / Pet Battles - World of Warcraft Forums (blizzard.com)
There are other guides on the pet battle forum.
In particular, look for posts from Grainne, he / she is an expert.
See this site for discussion of news, strategies for various fights, a tool to browse through your collection of pets, etc:
https://www.wow-petguide.com/
There are several other sites as well.
Welcome, etc.