We are multiplying 76 by itself three times: 76 · 76 · 76.
Because 76 appears 3 times, we write this using an exponent: 763. Here 76 is the base and 3 is the exponent (power), which tells how many times to multiply the base by itself.
So:
76 · 76 · 76 = 763 = 438,976
Steps: 762 = 76 · 76 = 5,776, then 5,776 · 76 = 438,976.