When my Mac book pro 2011 says no updates are available how to update latest version to iTunes or other apps . Please resolve this issue

Back up your data, check your applications for compatibility, and click on High Sierra. It's a full-version upgrade and won't appear in the Updates list.

Software requiring Mojave or newer can't be run on that Mac model.

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Products will over a certain period of time won’t be able to handle the new features future updates will provide meaning that you will need to upgrade if you want to update your device further. Like you said it’s 10 years old you can’t expect it to always be able to keep up to date.