100 div 3 = 33 r 1; 
 33 div 3 = 11 r 0;  
 11 div 3 =  3 r 2;
  3 div 3 =  1 r 0;  
  1 div 3 =  0 r 1

Converting Base 3 to base 7

Checking the answer:

102013 = 1 × 34 + 0 × 33 + 2 × 32  + 0 × 31 + 1 × 30
       = 1 × 81 + 0 × 27 + 2 × 9 + 0 × 3 + 1
       = 81 + 18 + 1 = 100

To convert from a representation in base three to a representation in base seven, use base ten as an intermediate:

____3   ———>    ____10   ———>   ____7