How much quantity and What are the ingredients we need to cook mughlai chicken biryani for 100 persons

Look up websites that help with "cooking for a crowd."
They usually give recipes for 50 or 100 people.
Look at a regular recipe for Mughlai chicken recipe and see how much meat it specifies.
Divide the "cooking for a crowd" chicken amount by the "one time" chicken amount, then multiply the single recipe by that factor.
(Or, if you will have walk-ins, first do the above multiplication and then add 10 to 15%.)
One caution - in translating home recipes to large quantity, it is safer to use initially a lower factor for multiplying spices, as they can be strong. When cooking the big dish, taste and - if needed - add more. Always easier to add more, than to fix an over-spiced expensive set of ingredients.
Good luck with your event!