I have a circuit that I have implemented from a research paper in LTSpice. I want to now implement it in hardware like breadboard and then on PCB zero maybe. I had some doubts since I am a beginner, like how do I power the op-amp, generate the volatges in mV, and the current in mA. If anyone can please reply then I can get into in details. Thank you.

 

How stable and accurate do the mV and mA sources need to be?
What resistor value tolerance is allowable?
Have you considered op-amp limitations/characteristics, such as input bias currents, slew rate?
Do you have a budget for this project (which might affect your choice of op-amps etc)?

 

how do I power the op-amp

You use batteries or a power supply.

generate the volatges in mV, and the current in mA.

Voltage and current for what purpose?