You have the ability to take a Purchase Order created in SI 2017 and export it to QuickBooks if you wish.
Select the Purchase Order in the Purchase Order Explorer and click the [Create Purchase Order] button in the QuickBooks section of the ribbon:
This will open the Create Purchase Order form:
This form is identical to the form when using the QuickBooks Purchase Order functionality directly within Projects, with one exception. When initiated from the Purchase Order Explorer, QuickBooks Purchase Orders will utilize the Unit of Measure field for Products and will automatically adjust the quantities for Products where a unit of measure has been set.
Example: The following wire is set to be Bulk Wire so it is priced by the foot but it is bought in spools of 500 feet:
When added to a Purchase Order from a Project where there is a total of 1050 feet of wire, the quantity to order will be 3.
Click here for full details on creating a QuickBooks Purchase Order, skip to step 5.