Switch the old iPad

if purchased through Apple, in most places there is a 14 day

period during which you can return the iPad for a refund;

check with Apple for the location where you mad the purchase.

If purchased through a retailer other than Apple, their return policy will govern.

Time limit starts with purchase, not with date of first use.

I presume that you are looking to establish a potential trade-in value for your old iPad:

Apple Trade In - Apple