A family of Microsoft word processing software products for creating web, email, and print documents.
Thank you for providing the version number, Kevs22. It seems that you currently have an Office 2019 retail license. I'm not sure if the dictate feature is available on the current version you have, as the link I provided above said that it is only available for Office 365 insider subscribers. You can also try following the steps provided by a community user, "Mia Zhao MSFT," where the user stated to "Go to System Preferences > Keyboard or Dictation and Language > Dictation. On the left side, under the microphone icon, select Internal Microphone instead of Auto or External Microphone," and another user seconded that these steps work. You may also try double-pressing the fn key on your keyboard and check if the microphone icon will pop up or if it starts to dictate. In case the issue still persists after trying the suggested steps, it might be that your version does not have the dictation feature.
I pulled the above steps from Official Microsoft Support website. For reference, here's the link below:
https://answers.microsoft.com/thread/b682f170-a4c6-4469-8ef5-3ea7c3cf819b
In case you still need further assistance in the future, please don't hesitate to let us know. We the community user just like you are always here trying to help. Thank you, and have a nice day!