how to up-date the system of a MacBook Pro (13-inch, Early 2011)?

A MacBook Pro from early 2011 can only be upgraded to macOS 10.13.6

Further upgrades are not supported by the hardware.

If you haven't installed macOS 10.13.6, check this article about how to do that:

How to download macOS - Apple Support

Follow the steps in this article, to start up in Recovery mode and install the latest macOS version for your MacBook Pro Mid 2010, which is macOS 10.13, High Sierra.

How to reinstall macOS - Apple Support

Or check the link to download macOS High Sierra in this article:

How to download macOS - Apple Support

I have a MacBook 13" mid2010 and I want to update the os system and

don't know where or find the software