What should i add at path Command : to Cron, with Plesk v12.0.18 . OS Debian 7.8

[MoldovanL]

Hallo

I'm a beginner. I rented a server with OS Debian 7.8 and Plesk v12.0.18 . for my site but no technical support is provided. I have to solve any problem myself.
I want to run Cron, at 10 minutes but Looks like cron is not run on webserver.

What have I done: I am a beginner and I searched the internet
I saw hier my v Plesk Panel: https://conetix.com....n-job-plesk-12/

1) click domain-> Open in Control Panel -> Scheduled Tasks -> Add Task and then

Minute * = */10
Hour * = *
Month = *
Day of the week = *
Command * = .......... and Here ?

The path on my server is: /var/www/vhosts/Site.com/httpdocs/_cron/cron.php
I set for the cron, my mail and i receive this:

/var/www/vhosts/site.com.../httpdocs/_cron/cron.php: 1: /var/www/vhosts/site.com.../httpdocs/_cron/cron.php: cannot open ?php: No such file
/var/www/vhosts/site.com.../httpdocs/_cron/cron.php: 2: /var/www/vhosts/site.com.../httpdocs/_cron/cron.php: Syntax error: word unexpected (expecting ")")

What would be the correct path?

Can you help me pls?

Thanks in advance.