How can I create my own UPC barcode?

You need to do 2 things first buy cheap UPC Codes from

https://codesforamazon.com/product-category/barcodes/upc-barcodes/

then create barcode for those codes at

https://www.zoho.com/inventory/free-barcodhttps://www.zoho.com/inventory/free-barcode-generator/e-generator/

hope it will help you to solve your problem.