Be sure you read the limitations of the desktop to QBO process, especially concerning payroll.  And be aware that desktop payroll will have to be canceled and QBO payroll subscribed to and set up

https://community.intuit.com/articles/1146059-import-limitations-why-some-data-doesn-t-come-over-fro…

Resolution for 'backup version issue: 'How to transfer files from a desktop backup version to the online' available: Yes.

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

For more information about resolving issues related to backup version in Quickbooks/QBO or to get support for the issue 'How to transfer files from a desktop backup version to the online', click the link below: