Updating from OS X El Capitan to Sierra

Yes. Or High Sierra if you'd prefer. I know I would.

Can I update from OS X El Capitan to Sierra? I have a MacBook Pro 13" Late 2011 model

If you can run macOS 10.12 Sierra, you can run macOS 10.13 High Sierra

macOS 10.13 High Sierra - Technical Specifications:

https://support.apple.com/kb/SP765?locale=en_US

How to upgrade to macOS High Sierra

https://support.apple.com/en-us/HT208969

MacBook (Late 2009 or newer)

MacBook Pro (Mid 2010 or newer)

MacBook Air (Late 2010 or newer)

Mac mini (Mid 2010 or newer)

iMac (Late 2009 or newer)

Mac Pro (Mid 2010 or newer)

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https://itunes.apple.com/us/app/macos-sierra/id1127487414?ls=1&mt=12

macOS Sierra requires at least 4 GB of RAM and 8 GB of storage space and will run on:

• iMac: Late 2009 or newer.
• MacBook and MacBook 12-inch: Late 2009 or newer.
• MacBook Pro: Mid 2010 or newer.
• MacBook Air: Late 2010 or newer.
• Mac Mini: Mid 2010 or newer.
• Mac Pro: Mid 2010 or newer.
• Xserve is no longer compatible.

https://itunes.apple.com/us/app/macos-sierra/id1127487414?ls=1&mt=12