Um, why isn't it "Raj juraab nahin pehanta hai?"
'Hai' is optional in negative sentences with 'nahin'. That said, it is not wrong to include it.
Raj juraben nahin pehanta. It should also be accepted.
जुराब is masculine so its plural is जुराब itself.
That said, since जुराब is not a very commonly used word in Hindi (मोज़ा is the more popular synonym), जुराब is sometimes incorrectly used as a feminine noun so you may see जुराबें being used.
Socks is mooja ig
Raj will get shoe worms if he doesn't wear them