How to auto-number orders linked to specific stores?

Question

Django

When creating a new order, it is necessary that the numbering of those linked to stores (categories) takes place. Suppose, if from one store, then the numbering should be as follows: m1, m2, m3 ... etc.
With another, similarly, only the letter is different. I don't know how to implement it....

Answer 1

manually calculate the number. such logic.
create a maxnum table with fields idshop, num
increment num for the required idshop on each insert