Hi, help please

I'm not sure whether this is the correct place. But I would like to show my question about my MacBook here. The Mac system caught SuperAdRemove ads last week. Firefox and Safari are messed up by numerous ads. I spent a few days but found out methods or posts providing step-by-step guide in Windows issues. Do you have any idea how I can restore my Macbook as it used to be? Thanks in advance!

Hi, I have a desktop that doesn't have WiFi abilities. What equipment can I buy that will allow me to use wifi? Please include a picture so I will know what it looks like when I make my purchase. Thank you for your assistance.