Converting a number from a 5-decimal number system to a 7-decimal one?

Question

Number systems

How numbers from different number systems are universally translated,
At the moment I am doing the following algorithm of actions:
number from 5CC -> 10CC -> 7CC

Answer 1

Determine in the 5th system what is the maximum digit plus one ("ten" roughly speaking) of the 7th system (10-/7 = 12-/5);
divide the 5th number by 12-/5 several times until there is a number less than 12-/5;
the resulting remainders, including the last one, will be the digits for the 7th number;
all.