A different approach...
In the above, are you referring to getting the IPB v3.x installation working before proceeding to do an upgrade? If so, you're going to need to ensure that you have a version of PHP that is supported by v3.x - which will mean PHP 5.x, as PHP 7.0 and above won't work.
Incorrect - PHP 5.6 or lower, depending on the version of 3.x. I may 'work' but it wasn't officially supported and was never required.