Hi @amirhosein
First thing first, you have to create backup of whole site, including database, as i can see, you are using Cpanel so this shouldn’t be a problem (there is automatic script in Cpanel for creating backup, after that you just have to download it to your computer).
- upgrading process is same for 2.3.7 to 2.4.x and to 3.0.0 and can be done without CLI access (although shared hostings have CLI access from web applications).
2.1 to start upgrading (after you have created and downloaded your full backup of site files and database), you have to delete all files in directory except config.inc.php, and folders public/ and /files (folder where your files are stored, you can find this information in config.inc.php).
2.2 Download full package from ojs site https://pkp.sfu.ca/ojs/ojs_download/ and extract it to your computer, delete config.inc.php, and folder public and compress it again and upload to server (or don’t compress and upload to server via FTP)
2.3 in config.inc.php (on server side) change installed from on to off and save.
2.4 in web browser, go to journal address and instead of install click to upgrade (that would be first option you can select au page).
2.5 wait for upgrade process to complete and after that change config.inc.php install to on and that should be it and go to journal page (it should be upgraded).
To upgrade from 2.4.x to 3.0 repeat same process again, but my recommendation is not to keep old config.inc.php, you should update new file and copy it to server.
More about update and upgrade process you can find in upgrade documentation