My calculations are as follows:
Fuel consumption=> 2ml/Kw-hr
PLF=> 0.8

Plant capacity =>4000 MW

Fuel consumption per day=> 4000 x 2 x 0.8 x 24 =153600 Lit/Day
Considering storage capacity for 60 days
=> 153600 x 60 = 9216 KL

I have considered 3x2500KL HFO storage Tak & 2x1000KL LDO Tank