See, if you buy in CNC and convert it to MIS and then square-off, it is Intraday trade and charges will be accordingly, which you can calculate here here. There are no charges for converting your position from CNC to MIS.
Also, if you buy using CNC and sell on the same day, even then it is considered as Intraday trade and charged accordingly.
In this case, suppose you have bought 10 shares using CNC and convert 5 to MIS and square-off and take remaining 5 for delivery then Intraday charges will be on 5 shares which you converted and squared-off while 5 will be considered as delivery trade.