Unfortunately, it is not possible to upload a barcode list to Shopify for selling tickets. Your events are already set to include unique QR codes on the tickets that your attendees purchase. You have the option of uploading a barcode on your tickets but it will be the same barcode for all the tickets purchased instead of a unique QR code.
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To set this, you can go to the event, then on the event dashboard click on Event settings.

Now on the Event settings page, click on the Tickets tab

On the Tickets page, scroll down to the ticket types, first, we’ll work on the Online Ticket Page.

Click on Customize.

This will send you to the Online Ticket Page settings.

On the Online ticket page settings, click on Ticket info.

On the Ticket Info page, click on Ticket Formats.

On the Ticket Formats page click on Barcode.

This is where you should be able to upload your barcode. Under Settings, on Custom image, click on Select file to upload the barcode.

Now we’ll go to the PDF Ticket page, and click Customize.

On the PDF Ticket settings, click on Ticket

On the Ticket page, click on Ticket Stub.

On the Ticket Stub window, click on Code.

On the Code page is where you can upload your barcode.

Unfortunately, there is no option to change the QR code to a barcode on the Apple Wallet Pass ticket.