Need help regarding borewell filled with mud

What to do if borewell is filled with mud

Hello Sir,

I have drill borewell of 380 ft. and got water for 2 .1/2 inch at 345 ft, but now the borewell is filled sand upto 330 ft. Can you please suggest, what I have to do now, do I have to put inner casing after flush, how much inner casing I have to put, I remember I got loose sand at 95 ft to 100 ft is this causing problem, please help thanks.