When trading-in an unwanted device, you will always receive significantly less for it than you paid. If your iPad is relatively new, without faults and in good condition, selling the iPad privately (e.g. eBay) might be a better option - potentially recovering more of your initial financial outlay.
Before disposing with your iPad, ensure that it is properly prepared and erased before it leaves your possession:
What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
As for Apple trade-in, you can establish eligibility and potential value in your country/region here:
Apple Trade In - Apple