How to obtain negative and positive voltage (±16V) for LM324N
The simplest way is to get a 32v power supply then create a virtual ground halfway between VDD and GND. This can be done with a simple resistor divider, or by using an op amp, possibly buffered with mosfets.

Another option is to purchase a self contained power supply that provides positive and negative output. I didn't see any in my brief search that provide +/- 16, but I found many that provide +/- 24v, for example: https://www.digikey.com/product-detail/en/cui-inc/PEM1-S5-D24-S/102-3031-5-ND/4006999