Automatic unit conversion for inventory item

Customers buy most of the stuff in cases and the cases comes with sleves in it and each sleves has certain items in it.

For example, they buy a case of paper plates. Each case comes with 6 sleves of paper plate in it and each sleve has 50 plates in it.

When they count for inventory, they need to count the left case, left sleves, left plates and then they need to mannually convert everything into case and input that number in adjust inventory section because the buying unit is made according to case.

They want the system to automatically calculate the conversion for them once they set the conversion unit in the back office.

So, they mean they can just input the number of plates, number of sleves and no of case left and system will automatically convert everything into buying unit which is case.