3.9 * 10^33 is Scientific notation for :
3,900,000,000,000,000,000,000,000,000,000,000 or
3.9 decillion.
When you have scientific notation just know, that after the decimal, there will be the exponent of 10's number of digits. In this case there are 33 digits after 3: 9 followed by 32 zeros.
Hope this helps!