Is oaks a common noun

Yes, the Word 'oaks' is a common noun, the plural form for the singular 'oak', a Word for a type of tree, any oak tree anywhere.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Annie Oakley (1860-1926), star of the Buffalo Bill Wild West Show
• Fair Oaks, CA
• The Oaks at Ojai (spa), Ojai, CA
• Oak Brand Leather (saddles and riding gear), Oklahoma City, OK
• "White Oak", 1921 movie with William S. Hart
• "The Oaks", a novel by Patrick Brown