During my first use of Meta, I was unable to save my private key and 12 words, and after reinstalling the metamask in Chrome, I was unable to log in. Only the private json file and password are known.If I can't log in, how can I find my private key in my json file or data stored on my computer? Please help me
If your account was created in MetaMask, then 12 word seed phrase was the only way to restore it. If you have a hard drive backup, that could help.
If your account was imported into MetaMask using a JSON keystore, you can re-import it into any instance of MetaMask once you set it up again (configure a new password, etc).
Make sure to backup your seed phrase next time!