Amresh,
The Firm-Planned Production Order shows yo are manufacturing an Item with a UOM of PIECES. Now we need to look at the Line Components that each UOM = PIECES or their relevant UOM and an Item UOM conversion to PIECES.
My example below shows PCS except for Bell Item. This uses BOX and have an Item UOM conversion for PCS

Check this to make sure your components UOM will process with a Manufactured UOM = PIECES.
Thanks,
Steve