i bought a used ipad from used market and there is an icloud on the device .. and no way that i can contact the owner .. what can i do

Absolutely nothing.

Return from where you purchased and attempt to get your money back or recycle it responsibly.

That iPad is a dead, useless device to you.

No one here can help you and Apple will not get involved and help you, either.

Next time, purchase a new iPad from Apple or a discounted, refurbished iPad from Apple’s Refurbished & Clearance section of Apple’s Website or a new or refurbished iPad from an Apple authorised, third party retail or online reseller OR other trusted sources for new or used Apple products.

If you must purchased used devices from unknown sources, you must ask more questions of the iOS device seller, ask for more photo/images, ask if the iPad has user/iCloud activation lock and ask for photos/images/short video proof that such an iPad has been reset factory settings and shown proof of the iOS device's start up screen showing the animated, moving, multi-language “Hello” Welcome to iPad screen.

If the iOS device seller is unwilling to do all of this, pass on the iOS device and look at other iOS device sellers.

Sorry & Best of Luck to You!

Return for a refund or recycle it.