Hello David,
a backup of the forum consists of three parts.
The first part is the database.
The second is the forum software with the configuration files.
The third part is the directory with the attachments and the CSS Files.
You wrote about a 72 Mb database. You can save it via “Forum Maintenance‘’ in the Admin Panel. There you have the option of backing up the database with or without the table structure. I would always back up the version with the table structure. I personally think a backup via phpMyAdmin is better.
The second part is the forum software. You can download the appropriate version of the pure forum software at
https://www.simplemachines.org and reinstall it according to the instructions.
SMF 2.0.17 requires PHP 7.3
What is still missing is the attachments directory and the CSS Files from the old forum. This is always the largest directory in a forum, as all images and attachments are collected there. The directory must be completely backed up and restored. The structure created by the SMF forum is important here. It is therefore best to compress the entire directory and back it up in this way.
So you need the database and the directories with attachments and avatars from the old server
ralf