Re: Create manually triggered flow for SharePoint list item to download all attachments to target folder (One Drive)
Hopefully this is what you are after. I wasn't sure if you also wanted to create a folder using the Barcode Number in addition to prefixing the file names but have done that here. If you didn't want the folder, then you can just create the files directly into your destination folder that already exists.
The source list in SharePoint for this example has three attachments.


And the destination folder in OneDrive is:

The full flow is below. I'll go into each of the actions.

For a selected item is setup for the source list in SharePoint so you can select an item and trigger the flow.

Create new folder will create a folder in OneDrive using the fileName from the trigger.
Since we are using the Title column for our Barcode Number, we can just use fileName from the trigger. If we wanted to get data from another column, we would need to use a separate Get item action, but no need here.

We use Get attachments to get the attachments associated with the list item.

Next, we setup an Apply to each to iterate through each of the attachments.

Get attachment content gets the actual content we need to create each attachment file.

Finally, we use Create file to create the attachment file in the folder we created earlier in OneDrive and prefix each file with the Barcode Number using fileName from the trigger.

The final output in this example is below.
