In a certain code language "PRINCE" is written as "356987". In that code…

Step 1: From the given code, map each letter in 'PRINCE' to its corresponding digit:

P → 3, R → 5, I → 6, N → 9, C → 8, E → 7

Step 2: Now apply the same mapping to the word 'NICE':

N → 9, I → 6, C → 8, E → 7

Step 3: Combine the digits in order: 9, 6, 8, 7.

Therefore, 'NICE' is written as '9687'.