I have one field that is named as Hour. It is in 12 hour format like (12Am, 1AM, 2AM and so on till 11Pm).

[KommulaRahul]

How to convert to 24hour format like (0, 1,2,3 till 23) 

[Chanty4u]

Try this

    Time#(Hour, 'hA') AS Hour24

[BrunPierre]

This perhaps?

Time(Time#(Hour, 'hhTT'), 'h') as [24Hrs];

[KommulaRahul]

It is showing only from 1 to 14 hour 

From 15 to 24 it is showing

[KommulaRahul]

I mean from 15 to 24 hour is not displayed. 

Only from 1 to 14 hour is coming