Hey @Oneadrian111, welcome to the MetaMask community!
If you have your Secret Recovery Phrase, you are able to access and recover your MetaMask wallet, which can be used on Avalanche through adding it as a custom network. If you have your Secret Recovery Phrase, you do not need your private key to recover your wallet. Regardless, here is more information on how to find your private key in our Knowledge Base:
Also more information on Avalanche on MetaMask:
For the error when trying to unlock your wallet with your password, try using another browser and/or resetting your cache. Here is more information on our Knowledge Base: