Something does not sound right here.
You cannot upgrade from Joomla 3.9 to 4. You would have to first upgrade to Joomla 3.10.
Moreover, Akeeba Backup 7.0.2 was released well over 2 years ago. It was never compatible with Joomla 4 stable, it was only compatible with some early alphas and betas.
So, first, verify your versions.
If the versions are correct we'll have to do it the Hard Way™.
First, delete the files:
These are Joomla's cached copies of the installation scripts for the old Akeeba Backup package, the old Akeeba Backup component and the defunct installer plugin which will be removed from your site. These prevent the uninstallation.
Uninstall the Akeeba Backup package, version 7.0.2.
Delete the tables:
They are left behind because we removed the installation script from the component, therefore it doesn't know which tables to drop on extension uninstallation.
Uninstall FOF 3.
Since we removed their installation scripts they will uninstall without checking for dependencies or the Joomla version.
Finally, install Akeeba Backup 9 again, twice in a row, without uninstalling before or in between. This makes sure that any errant plugin removal will be undone and AB9 will be back in working order.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!