That toolbox is one of the toolboxes in the Student Suite bundle. However in every other case it is an optional extra cost including the case of purchasing the non-bundle Student Version .
Another of your postings suggest you upgraded versions, by more than one release. That could suggest that you purchased a new license, in which case you might have accidentally purchased Student Version instead of Student Suite.
The function 'dataset' is a function in the Statistics and Machine Learning Toolbox. You must have that toolbox installed to use it. The error message would susggest it is not installed.
Type the command 'ver' in you command window to see what products are installed.
If you have access but it is not installed, you can use the Add-Ons explorer (Home Tab under Environment) to install it.
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