To reset your passcode, you can restore your iPad Mini through iTunes.
First, you will need to put the iPad into recovery mode using these steps. (https://support.apple.com/en-us/HT204306)
1. Disconnect all cables from your device.
2. Hold down the Sleep/Wake button, then "slide to power off" to turn off your device.
3. Press and hold the Home button and plug the device into your computer. If your device doesn't turn on automatically, turn it on. Don't release the Home button.
4. Continue holding the Home button until you see the Connect to iTunes screen.
Then, connect your iPad to your computer and open up iTunes, then click Restore iPad and iTunes will restore your iPad (from a backup if you have one, otherwise to factory settings).
Best of luck!