Please make sure you have uploaded the these custom file over your whmcs root path.
Step 1: Next step you need to follow is rename it so that these files can be executed.
[ privacy-policy.php_new -> Rename file to -> privacy-policy.php ]
[ refund-policy.php_new -> Rename file to -> refund-policy.php ]
[ terms-of-service.php_new -> Rename file to -> terms-of-service.php ]
Step 2: Now go to following path so that template files too renamed
Path -> templates/clientx-child/custom_files/
Step 3: Next step you need to follow is rename it so that these files can be executed.
[ privacy-policy.tpl_new -> Rename file to -> privacy-policy.tpl ]
[ refund-policy.tpl_new -> Rename file to -> refund-policy.tpl ]
[ terms-of-service.tpl_new -> Rename file to -> terms-of-service.tpl ]
Note: You need to only remove the _new suffix from files in both cases.