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As per https://www.akeeba.com/documentation/akeeba-backup-joomla/restoring-backups.html#general-guidelines

Do not try to overwrite one Joomla! version family with a different one. Overwriting a major version with another (e.g. restoring a backup taken on Joomla! 3.7 on top of a site running Joomla! 2.5 or vice versa) or between different minor versions (e.g. restoring a backup taken on Joomla! 3.7 on top of a site running Joomla! 3.6 or vice versa) will NOT work. Joomla! moves files around between minor and major versions. Since the backup does not delete files not present in the backup archive this will end up with Joomla! being "confused" and malfunctioning. In these cases you should delete the existing files and folders (except, perhaps, user generated content) before restoring the backup. You can safely restore a sub-minor (path-level) version on top of another. For example, you can safely restore a Joomla! 3.7.5 site on top of a Joomla! 3.7.3 site or vice versa.

Before restoring the Joomla! 5.1 backup, you need to delete the files and folders of the Joomla! 3.10 site.

If you have already done that, com_akeeba is version 8 or earlier for Joomla! 3, com_akeebabackup is version 9 or later for Joomla! 4 or later. See https://www.akeeba.com/documentation/akeeba-backup-joomla/migrate-j3-to-j4.html