Generate Gate pass number based on Plant number

Hi experts! Here's my scenario.

I've created a module pool screen in which I'll give inputs of materials loaded in the truck which is going from one plant to another. So, after giving inputs I click on save and a gate pass number should be generated based on plant.
Ex: Plant 1001 gate pass number range should be 10000001 to 19999999
Plant 2001 gate pass number range should be 20000001 to 29999999
Please help me with relevant documents or sample codes. Appreciate your help.