There is no script to upgrade Jahia 6.6.2.7 to DX 7.1.0.0 without going through the upgrade to Jahia 6.6.2.10.
This is mandatory to upgrade from Jahia 6.6.2.7 to Jahia 6.6.2.10 as mentioned in our documentation at the following link https://www.jahia.com/extranet/jahia-xcm-version-66/migrate-to-digital-experience-manager (MIGRATION PATH)
Here is the interesting extract:
If your current Jahia 6.6 version is prior to 6.6.2.10, please upgrade it first to 6.6.2.10 by applying the corresponding migration packages.