Step 1: The exponent for 10 is 120. Since the exponent is positive, we must move the decimal point of a number 7.8 120 places to the right.

7.8 → 7.8-----------------------------------------------------------------------------------------------------------------------.

Step 2: Now we just need to replace empty spaces (dashes) with zeros and to delete old decimal point (the black one) to get:

7800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000