What type of processor socket does the Lenovo IdeaCentre K300 have, and can anyone recommend a good graphics card for this computer?

I''m trying to rebuild an old 2011 Lenovo IdeaCentre K300 desktop computer. Right now I'm trying to upgrade the processor and get a good graphics card for it but I've been having trouble finding out information of the model for this computer. Lenovo does not have any information on their website or in the owner's manual and it's hard finding information about the computer online.

Added (1). As what skeptic asked, yes this is the model.
https://www.cnet.com/...gb-640-gb/

Guest

Do you mean this one?:

You do realize that you'll become more frustrated while trying to rebuild/upgrade it. The LGA 775 socket is generations old. It would be for the best to yank out the entire innards and start with a mobo from this generation.

skeptic