34947ABCD.EF123993 hex (base 16)
D*16^0 = 13*1 = 13 decimal
C*16^1 = 12*16 = 192
B*16^2 = 11*256 = 2,816
A*16^3 = 10*4096 = 40,960
7*16^4 = 7*65536 = 458,752
4*16^5 = 4*1048576 = 4,194,304
9*16^6 = 9*16777216 = 150,994,944
4*16^7 = 4*268435456 = 1,073,741,824
3*16^8 = 3*4294967296 = 12,884,901,888
E/16^1 = 14/16 = 0.875 decimal
F/16^2 = 15/256 = 0.05859375
1/16^3 = 1/4096 = 0.000244140625
2/16^4 = 2/65536 = 0.000030517578125
3/16^5 = 3/1048576 = 0.00000286102294921875
9/16^6 = 9/16777216 = 0.000000536441802978515625
9/16^7 = 9/268435456 = 0.0000000335276126861572265625
3/16^8 = 3/4294967296 = 0.00000000069849193096160888671875
Add them all up to get 14,114,335,693.93387183989398181438446044921875 decimal.
To convert to octal, start by finding the largest "factor of 8" that will be less than 14,114,335,693.
8^11 = 8,589,934,592 (which is lower) and 8^12 = 68,719,476,736 (which is too high) so we start with 8^11 (12 octal digits).
2 * 8^11 = 17,179,869,184 > 14,114,335,693 so the first digital must be 1. 14,114,335,693 - 1 * 8^11 = 5,524,401,101 remaining.
8^10 = 1,073,741,824 and 5*8^10 = 5,368,709,120 so the second digit is 5. 5,524,401,101 - 5*8^10 = 155,691,981 remaining.
8^9 = 134,217,728 so the third digit is 1. 155,691,981 - 1*8^9 = 21,474,253 remaining.
8^8 = 16,777,216 so the forth digit is 1. 21,474,253 - 1*8^8 = 4,697,037 remaining.
8^7 = 2,097,152 so the fifth digit is 2. 4,697,037 - 2*8^7 = 502,733 remaining.
8^6 = 262,144 so the sixth digit is 1. 502,733 - 1*8^6 = 240,589 remaining.
8^5 = 32,768 and 7*8^5 = 229376, so the seventh digit is 7. 240,589 - 7*8^5 = 11,213 remaining.
8^4 = 4096 and 2*8^4 = 8,192 so the eighth digit is 2. 11,213 - 2*8^4 = 3,021 remaining.
8^3 = 512 and 5*8^3 = 2560 so the ninth digit is 5. 3,021 - 5*8^3 = 461 remaining.
8^2 = 64 and 7*8^2 = 448 so the tenth digit is 7. 461 - 7*8^2 = 13 remaining.
8^1 = 8 so the eleventh digit is 8. 13 - 8 = 5 remaining.
8^0 = 1 so the last digit is the number 5.
So far we have 14,114,335,693 decimal = 151121725715 octal. The same must be done with the fractional part of the decimal number (.93387183989398181438446044921875).
The binary (base 2) conversion can be done the same way.
BTW - The scientific calculator that is built into Windows can do the integer number conversions to/from hex/octal/decimal/binary in the blink of an eye.
This should get you started. Enjoy.