No. system

I could partially do it...

7 ^1 = 7
7^2 = 49
7^3= *43
7^4= *01
from 7^5, pattern gets repeated.
7^5= *07
7^6= *49 ... and so on.

The question states 7¹⁸⁷.
187 % 4=3. Therefore, the 3rd category will be the number.

So, 7^187= *43.

So, when divided by 800, it leaves a remainder *43.

But I am not being able to find out the first digit '3'.

Thanx...

343