can i use a 36 watt usb charger for my ipad mini 4

If it is an Apple or MFI certified charger (with the appropriate Lightning to USB or USB-C cable) , then yes, you can.

The charger doesn’t “push” power; it just supplies the power “drawn” by the device.

Regards

Giulio

There is no technical benefit to using a high-wattage Power Adapter with your iPad mini4.

Your iPad mini4 has a maximum charging rate of 12W (i.e., 2.4A @5V). Whilst you can safely use a standard USB Power Adapter rated at greater than 12W, your iPad will charge no quicker.