If you want to create a purchase order but you have multiple products to input at once, instead of inputting the product manually on the Buy menu, you can use the import function in the Buy Menu.
Step 1. Go to Buy Menu then click the upload button.

Step 2. In the upload file button, there will be a sample CSV file. You can download and use it as a template for importing your product.

*Sample Format CSV File.

Step 3. Click Choose file, select the CSV file that you've updated with your product's data from your drive, and click Ok.

Step 4. Result Upload multiple products

Upload multiple products using Excel / CSV when Buying (Create Purchase Order) Tutorial Video
You might also like to read these related articles below:
If you want to import sales orders via CSV file you can also check this article How to Import Sales Order via CSV File
If you want to set the purchase order fulfillment later, you can check this article Purchase Order Fulfillment Later
To set Differentiate Sales order and Invoice Number you can also check this article How to differentiate Sales Order and Invoice Number