thank you very much for your answer doncamilo
This is the result of zentyal.log:
2019/06/20 14:11:19 DEBUG> Backup.pm:1004 EBox::Backup::_checkZentyalVersion - Could not restore the backup because a mismatch between its Zentyal version and the current system version. Backup was done in Zentyal version 5.1.1 and this system could only restore backups from Zentyal version 6.0 at Could not restore the backup because a mismatch between its Zentyal version and the current system version. Backup was done in Zentyal version 5.1.1 and this system could only restore backups from Zentyal version 6.0 at /usr/share/perl5/EBox/Backup.pm line 1004
EBox::Backup::_checkZentyalVersion('EBox::Backup', '/var/lib/zentyal/tmp//backup.TZcEus') called at /usr/share/perl5/EBox/Backup.pm line 849
eval {...} at /usr/share/perl5/EBox/Backup.pm line 838
EBox::Backup::_unpackAndVerify('EBox::Backup', '/var/lib/zentyal/tmp/path', 'deleteBackup', 0, 'progress', 'EBox::ProgressIndicator=HASH(0x565257108ba0)', 'revokeAllOnModuleFail', 1, 'forceZentyalVersion', 0, 'dataRestore', 1, 'forceDependencies', 0, 'continueOnModuleFail', 0, 'installMissing', 0, 'modsToExclude', 'ARRAY(0x565256eac048)') called at /usr/share/perl5/EBox/Backup.pm line 1169
eval {...} at /usr/share/perl5/EBox/Backup.pm line 1163
EBox::Backup::restoreBackup('EBox::Backup', '/var/lib/zentyal/tmp/path', 'forceDependencies', 0, 'continueOnModuleFail', 0, 'installMissing', 0, 'dataRestore', 1, 'forceZentyalVersion', 0, 'deleteBackup', 0, 'revokeAllOnModuleFail', 1, 'progress', 'EBox::ProgressIndicator=HASH(0x565257108ba0)') called at /usr/share/zentyal/restore-backup line 105
eval {...} at /usr/share/zentyal/restore-backup line 104
2019/06/20 14:12:09 DEBUG> Backup.pm:1004 EBox::Backup::_checkZentyalVersion - Could not restore the backup because a mismatch between its Zentyal version and the current system version. Backup was done in Zentyal version 5.1.1 and this system could only restore backups from Zentyal version 6.0 at Could not restore the backup because a mismatch between its Zentyal version and the current system version. Backup was done in Zentyal version 5.1.1 and this system could only restore backups from Zentyal version 6.0 at /usr/share/perl5/EBox/Backup.pm line 1004
EBox::Backup::_checkZentyalVersion('EBox::Backup', '/var/lib/zentyal/tmp//backup.pdaCQx') called at /usr/share/perl5/EBox/Backup.pm line 849
eval {...} at /usr/share/perl5/EBox/Backup.pm line 838
EBox::Backup::_unpackAndVerify('EBox::Backup', '/var/lib/zentyal/tmp/path', 'revokeAllOnModuleFail', 1, 'dataRestore', 1, 'forceDependencies', 0, 'installMissing', 0, 'deleteBackup', 0, 'continueOnModuleFail', 0, 'forceZentyalVersion', 0, 'modsToExclude', 'ARRAY(0x55c65c06a3f0)', 'progress', 'EBox::ProgressIndicator=HASH(0x55c65c0514d8)') called at /usr/share/perl5/EBox/Backup.pm line 1169
eval {...} at /usr/share/perl5/EBox/Backup.pm line 1163
EBox::Backup::restoreBackup('EBox::Backup', '/var/lib/zentyal/tmp/path', 'progress', 'EBox::ProgressIndicator=HASH(0x55c65c0514d8)', 'continueOnModuleFail', 0, 'forceZentyalVersion', 0, 'installMissing', 0, 'deleteBackup', 0, 'revokeAllOnModuleFail', 1, 'forceDependencies', 0, 'dataRestore', 1) called at /usr/share/zentyal/restore-backup line 105
eval {...} at /usr/share/zentyal/restore-backup line 104
2019/06/20 14:13:31 DEBUG> Backup.pm:1004 EBox::Backup::_checkZentyalVersion - Could not restore the backup because a mismatch between its Zentyal version and the current system version. Backup was done in Zentyal version 5.1.1 and this system could only restore backups from Zentyal version 6.0 at Could not restore the backup because a mismatch between its Zentyal version and the current system version. Backup was done in Zentyal version 5.1.1 and this system could only restore backups from Zentyal version 6.0 at /usr/share/perl5/EBox/Backup.pm line 1004
EBox::Backup::_checkZentyalVersion('EBox::Backup', '/var/lib/zentyal/tmp//backup.p738fv') called at /usr/share/perl5/EBox/Backup.pm line 849
eval {...} at /usr/share/perl5/EBox/Backup.pm line 838
EBox::Backup::_unpackAndVerify('EBox::Backup', '/var/lib/zentyal/tmp/path', 'dataRestore', 1, 'revokeAllOnModuleFail', 1, 'deleteBackup', 0, 'progress', 'EBox::ProgressIndicator=HASH(0x5576e0281b60)', 'forceDependencies', 0, 'installMissing', 0, 'forceZentyalVersion', 0, 'continueOnModuleFail', 0, 'modsToExclude', 'ARRAY(0x5576e028ee10)') called at /usr/share/perl5/EBox/Backup.pm line 1169
eval {...} at /usr/share/perl5/EBox/Backup.pm line 1163
EBox::Backup::restoreBackup('EBox::Backup', '/var/lib/zentyal/tmp/path', 'installMissing', 0, 'revokeAllOnModuleFail', 1, 'dataRestore', 1, 'progress', 'EBox::ProgressIndicator=HASH(0x5576e0281b60)', 'forceDependencies', 0, 'deleteBackup', 0, 'continueOnModuleFail', 0, 'forceZentyalVersion', 0) called at /usr/share/zentyal/restore-backup line 105
eval {...} at /usr/share/zentyal/restore-backup line 104
I see that the problem is because the backup is of version 5.1 and the new installation is 6.0.1 ...
Is there a way to restore an old backup in version 6?
Thank you!