Well you would most likely need to create a script for this. You could use this script here to import the photopost users into
vb but you would need to modify this because this is designed to import into a clean vbulletin install
Want to go from standalone to Vbulletin in Photopost?
You would of course need to move photopost and its database to the new server and then after modifying and importing the users need to realign the userid's using this script
Reassign userid's when switching integrations to VBulletin
However before you do that you would need to realign Photopost to integrate with vbulletin and there are several threads here if you do a search on the words switch integration which will pull up the steps I posted before.