Hello Abbfabb,
Thanks for reaching out to the Community page,
You can not upgrade from a QBSE to a QBO it would be a case of canceling the QBSE subscription and taking out a new QBO subscription. You can not export data out of your QBSE account just have to disconnect bank and reconnect it in the new account. The reason why you can not export anything out is because they are 2 completely different products.