What software should I use to open the .dat flles I've just downloaded the Bitcoin Core for Windows.

I can see several .dat file. What can I use to open them. i.e. Is there a way to view them in plaintext?

Also, which file is the blockchain file?

Thanks!
The .dat files are opened by Bitcoin Core, they are not supposed to be opened in plaintext. The blockchain will be in the blocks/ subdirectory. You can see a list of the files bitcoin core uses here:
https://github.com/bitcoin/bitcoin/blob/master/doc/files.md