Want to know how to upgrade CentOS

From the development environment built with VirtualBox+vagrant+CentOS6 I wanted to move to CentOS 7.5, but I had no experience, so I had a question.

I thought about how to do it as a pattern in my own way.
I would appreciate it if you could tell me the recommended ways to move the environment.

Upgrading the CentOS distribution is
I had the impression that it must be difficult because there is a big difference between 6 and 7.
Attempted to upgrade the CentOS from 6 to 7. | Mimura's Handbook

Currently, CentOS 7.2 environment was created with a separate project, so
Copy it and set it to 7.2→7.5 and
(If it is a minor update, will it have little impact?)
Move directories per site via FTP software.
The node_modules directory is clean because the host OS is Windows. I'm not sure if I can move.
I searched how it works to move directly between vagrants. The information could not be reached.

The development environment is a common website environment.
Apache with Virtual Host
PHP
MySQL
WordPress
Git
gulp.js
Node.js
npm
nvm
Sass
Regarding the above tools, I would like to make the version the latest stabilizer.

NIC settings for virtualbox are
Check the virtualbox gui tool → Settings → Network → Adapter 2 tab
The assignment item is set to Host Only Adapter.
When prompted, the Ethernet adapter VirtualBox Host-Only Network#
appears (both centos6 from and centos7 from).

Question

• If you have any experience with minor updates such as 7.2→7.5 of CentOS, I would like to visit you.
• I would like to know if there is an easy way to move data from a specific directory within the vagrant project.
• I would appreciate it if you could let me know if there are any recommendations other than the two patterns mentioned above.