If you purchased via a download, you should have received an email with that information.  If you purchased the CD, it should be on the box or CD sleeve.

http://support.quickbooks.intuit.com/Support/Articles/SLN41392

Resolution for 'CD sleeve issue: 'how I find my Quickbook 2015 pro desktop version license key?' available: Yes.

The CD sleeve 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 CD sleeve issue yourself by looking for a resolution described in the article. If it is a complex CD sleeve issue or you are unable to solve the issue, you may contact us by clicking here or by using other CD sleeve support options.

For more information about resolving issues related to CD sleeve in Quickbooks/QBO or to get support for the issue 'how I find my Quickbook 2015 pro desktop version license key?', click the link below: