Zenfone 2 - Z00AD (4GB ram, 32GB rom) - no update option

Hi

I bought Zenfone 2 - Z00AD (4GB ram, 32GB rom, 1,8Mhz), it works fine but I can't find software update option. Simply it is not where it supposed to be.
I would really like to update it because i heard that battery is better after update. Can somebody give me some advice?

MODEL NUMBER:
ASUS_Z00AD

BUILD NUMBER:
LRX21V.WW-
ASUS_Z00AD-2.19.40.18_20150612_1183_user
044030427_201501060109
0010000500001

Thanks a lot!