MacBook Pro (13-inch, Early 2011)

That Mac can run up to and including High Sierra, provided you have at least the minimum 6GB of RAM.

Much more information is available if you just provide some of what BobTheFisherman has suggested.

More information about what Mac and what MacOS and what amount of RAM and drive you have installed.

Also, why do you want to upgrade? Are you seeking advanced features or better performance or access for different Applications, or something else?

We have no idea what app versions or operating version you are currently running so it is hard to tell you what updates are available.