the easiest way to see if your running 2.0 or 3.0 is to look at the structure. Do you have a root folder called "admin" or is it "adm"?
root/admin is 2.0.x
root/adm is 3.0 and later
if there is a root/vendor folder, it is newer than 3.0.14
to find your php version, check your hosting control panel or create a new file on your website root called php_info.php
copy paste this code into the file and save it
browse to the file in your web browser
in order to find the specific version number ie.. 2.0.
23 or 3.0.
14, you will have to check your database php_config table for 'version' number either using phpmyadmin or searching a database backup with a text editor
Also a few cautions on your software choices.
do not just randomly grab a folder and move/copy it using FileZilla. Be sure it is set to use binary by default and not auto or ascii. It may damage/corrupt your files, esp images.
I have not used Dreamweaver in close to 20 years because back then it had a habit of writing 10-20 lines of repetitive html instead of simply editing a css class and it often changed file encoding.
imho the best free choices are WinSCP for FTP, Bitvice SSH for SFTP and Notepad++ for file editing. The default settings for these progs will not harm your files and they are super simple