OK,
1. Take a backup of the shop database for safety reasons.
2.Do a select query to see and confirm which orders you will be changing their status using this script
Select * from PurchaseOrder Where Potype IN (2,4) and Convert(Varchar(15),DateCreated,102) >='2017.02.17' order by ID
assuming you want to change status for all orders created on or after 17th Feb,2017.
If you are sure then you run the below to close all those Orders
Update PurchaseOrder Set Status=2 Where Potype IN (2,4) and Convert(Varchar(15),DateCreated,102) >='2017.02.17'
All the best