Typo in your post.To convert from octal to decimal, multiply each number by 8^(n-1), where n is the position from the right, then sum these terms together.
For example octal "321".
3 * 8^2 = 3 * 64 = 192
2 * 8^1 = 16
1 * 8^1 = 1
192 + 16 + 1 = 209.
To convert from decimal to BCD, just use 4 bits for each digit. For example 29 in BCD is represented as 2 in binary followed by 9 in binary. This becomes 0010 1000, which is literally 2-9.