Transfer of sites to another server / adaptation to the new PHP

Theres an ancient server with a bunch of similarly ancient sites. On the server is php 5.2.6. Sites are working, everything is OK.
You need to move all these sites to another server, where there is 5.6.4 (there are 7, but at least under 5.6.4). After the transfer, you need to test the work and make changes so that everything works correctly under the new version.
Specifically:
1. 2 forums on the woltlab.com engine (there is an instruction - https://blog.kill0rz.com/2015/04/25/wbb-2-3-6-und-php-5-6/ you can roughly estimate the amount of work on it)
2. 2 projects, each of 10-20 pages in html php. One uses a library to generate pdf.
3. One clean html, there everything will work without edits, just transfer.
Deadlines are not burning.
In the answer please let me know how long it will take you and how much it will cost me.