Make sure to tick the option Track lots or serial numbers in Settings > Configuration > Warehouse to be able to enter serial numbers. In the barcode interface (accessible from Warehouse > Operations > All Operations by clicking the barcode), you will receive your incoming shipments. 

In order to assign unique serial numbers, put the quantity of the corresponding product line to 1. Then click Create lot (at the right side of the line) and enter the lot / serial number. 

Now put that 1 unit in pack. 

Then do the same for the remaining quantities: always select 1 unit, create a lot / serial number and put that 1 unit in pack. That way, you will have a lot number for each unit.