is the simplest solution.
The schematic is published if you can't get it where you live and/or you want to build it yourself.
Any op-amp will do. You don't need a "power amplifier". Power amplifiers are designed to drive a speaker.NOTES:
A "rail-to-rail" op-amp is best if you are running from a single 5V supply.
The op-amp needs to be biased for 2.5V on the output, because the Arduino can't directly handle the negative half of the AC audio waveform. (R2 & R3 in the SparkFun schematic).
The electret mic needs to be biased/powered (R1 & C1).