Now, I believe you know how bases work-
suppose we are writing using base n. That means we have n digits that represent numbers:
0, 1, 2, ......n-1
for example, if n=2. we have 2 digits- 0 and 1.
Lets call the first digit the main digit (for example, the main digit in 11001010110 be 0, in 345 it will be 5 and so on)
If the digit d is K places to the left of the main digit, its value will be the base multiplied by itself K times, then multiplied by the digit. if the base is N it means the value will be d*NK. It also means that if the digit is K places to the right of the main digit, its value will be d*N-K=d/(NK)
for example, if our base is 10, then the value of the marked digit in 0.007 will be 7*10-3=7/(103).
If our base is 2, it means the value of the marked digit in 0.01 will be 1*2-2=1/(22)
So, if we want to convert 3.141592 to base 2, we have to use those rules. 3.141592 (base 10)~~11.0011
Unfortunately for you, pi is irrational, meaning we cant write it with a finite number of digits (i know you didnt want me to do that but i just had to say that)
you wanted me to write 3.141592 in base 2, and im afraid to tell you we cant write this rational number with a finite number of digits either! but we CAN write it as a Repeating decimal. why? because if you dont want a fraction to be a repeating decimal (lets say the fraction is m1/m2) then after reducing the fraction you need all of m2's factors to be factors of the base N as well. It doesnt work with 141592/1000000, but we can write it as a repeating decimal.
Can you to that?