QBO does not create or store bar codes for anything, you will have to use third party software like Zebra or something.  There are free bar code generators on the net, google for it.

a bar code reader is a substitute for a keyboard, it reads the code and translates it […]

Resolution for 'alphanumeric codes issue: 'How Can i connect barcode reader and label printer to QB to add my own barcode to my products?' available: Yes.

The alphanumeric codes issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the alphanumeric codes issue yourself by looking for a resolution described in the article. If it is a complex alphanumeric codes issue or you are unable to solve the issue, you may contact us by clicking here or by using other alphanumeric codes support options.

For more information about resolving issues related to alphanumeric codes in Quickbooks/QBO or to get support for the issue 'How Can i connect barcode reader and label printer to QB to add my own barcode to my products?', click the link below: