Shouldn’t you ask your teacher for help?¬†¬†Here is the support page for converting from qbdt to qbo:
https://quickbooks.intuit.com/move-from-desktop-to-online/

Resolution for 'Appendix issue: 'Looking for Appendix A at free online plus. Can I import from ? P54' available: Yes.

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

For more information about resolving issues related to Appendix in Quickbooks/QBO or to get support for the issue 'Looking for Appendix A at free online plus. Can I import from ? P54', click the link below: