How do I get the value of an auto incremented primary key(in an external mysql db) in flask pymysql?

Question

In my API route I am first going to run an insert statement for inserting into PurchaseOrder_002.After that, I need to insert into Lines_002 in my second sql statement for the poNo_002 value that I inserted into PurchaseOrder.

poNo_002 is an auto incremented primary key in PurchaseOrder table.For inserting into Lines how do I get the poNo_002 value?

databse ER diagram