I have a first generation IPad and an IPad Mini that I would like to trade in for 2 iPad mini 4. How do I find out what they are woryh

iPod and Mobile Phone Recycling Program - https://www.apple.com/recycling/ipod-cell-phone/ - Get an Apple Store Gift Card for the value of your old device.

Apple Recycling Program [all computer and mobile devices] - http://www.apple.com/recycling/gift-card/ - Some devices may be eligible for a gift card, others can only be recycled.

You can probably get more by reselling the device.

What to do before selling or giving away your iPhone, iPad, or iPod touch - https://support.apple.com/HT201351 - "Use these steps to remove your personal information from a device"

If you’re in the US, best buy and amazon have an online estimator that can give you an idea what they are worth.

You wont’ get an even trade, it’ll likely be more like a discount.

If you take them to an apple store you’ll get 10% of its value