You can ascertain if the purchase order needs to be placed or not, and the quantity to order while recording a purchase order voucher.
In the purchase order voucher, select the required stock item.
Press Alt+S to view stock query report.
In the stock query screen press F7 (Show Reorders) to view the reorder details. The reorder status related to the stock item appears, based on the reorder levels set.
Note: Similarly, while recording sales orders you can ascertain the reorder status of stock items.