In your cPanel > File Manager, click on and edit the wp-config.php file. Make sure there are no strange codes or anything unusual. If there is malware in this file, it will generally look like a long string of random text. You can compare it to the wp-config-sample.php file to be sure.
Now go into the wp-content folder. It should look like:
plugins
themes
uploads
index.php
Make a list of the plugins you are currently using, then remove the plugins folder and index.php file. You will need to re-install your plugins after the cleaning process.
Go into the themes folder, and remove any theme which you are not using. You will then need to individually check each file in your current theme to make sure there is no malware or strange codes in them. If you have a clean backup of your theme somewhere (like on your computer), then to be safe you should just delete the entire themes folder.
Check every directory inside your uploads folder to make sure there are no php files or anything that you may not have uploaded.