Installing and upgrading help

Although Howard already mentioned the main culprit being PHP 7, so switch to 5.6, then start upgrading, 2.0 > 2.2 > 2.7 (this is important as to upgrade to 3.x, you need to have 2.7 at minimum), then to 3.0.

if you manage to upgrade to 3.0.1+ then PHP 7 can be used (prefer 7.0.x version and not 7.1 or later).

This step wise up gradation will let you bypass the REQUIREMENT of Barracuda as file format in MySQL, else quick jumps will require it and on shared host you wont be able to convert file formats. make sure your DB language is set to UTF8_unicode