If I want to pay khums for all the inheritance from my father – which includes land, money in bank, jewellery, houses etc – how do i calculate the amount i need to pay? He did not pay Khums and I want to pay it now to make everything in the inheritance halal. Can you please guide me on that.

You have to evaluate the things that you inherited such as property and jewelry, and when you know the value of all, you can sell some of them and pay the fifth.
If the value of real estate is ten million, for example, and jewelry is five million, then the total is 15 million, and one-fifth of it is five million, then you can sell the jewelry and take out its value as a fifth, and the real estate is thus clean.