[Q] Nothing exists in '/ system' folder on my Kindle Fire. topic

Hello!
I have a big problem.
I tried to install custom ROMs on my otterx, and it occurred several kinds of errors.
So I tried to see what happens in otterx via file manager of twrp and paniced.

Nothing exists in '/system' folder! (Only 'bin' folder)

I have no idea to solve this problem.

plz help me

My kindle fire is 1st gen and twrp version is 2.8.1.0.

(Sorry, I'm not accustomed in English;;)