The Sonos software itself can’t read files stored on your iPad, however you can use the Apple Music app to AirPlay 2 to your Sonos speakers, assuming what you have is AirPlay 2 compatible.
 

Otherwise, the data needs to live where are your other music is, as expressed in this FAQ.

Thanks for the reply Airgetlam,

The iPad is AirPlay 2 compatible.

I don’t use Apple Music or other music services. 
All my music is stored in the files folder and accessed using VLC.

Shouldn’t Sonos software be able to access the files there if it has the correct path to the directory?

I’ve read the FAQ link you provided but it doesn’t cover iOS. or I am missing something.

No, Apple doesn’t allow Sonos (or anyone else for that matter) to access files stored on an iPad. They used to, but that changed in the iOS release back in august of 2019. This is why there are no instructions for iOS devices, they can’t be used as ‘Local libraries’. Android is finally going this route as well, most likely to Sonos’ chagrin. 

The device being AirPlay 2 compatible I was speaking of was the Sonos, not the iPad. Older speakers that were designed before AirPlay 2 existed don’t have the electronics necessary. As of (I think), the Sonos One, and everything since then is AirPlay 2 capable.

Remember, the Sonos ‘player’ doesn’t exist on your iOS device, it exists on the speaker. The controller is only a remote control as to what the speaker is doing. 

I don’t use VLC myself, but if it’s using the correct Apple API, you should be able to use AirPlay 2 to send the signal to an appropriate Sonos speaker. 
 

This FAQ may help you in using AirPlay 2 from your iPad to your Sonos One.

Thanks again for taking the time to help me. 
It is appreciated. 
Your answer helped me understand things much better. The link was informative as well. 
I’ve managed to get things sorted out now and everything is playing fine. 

Again thanks for your help. 
Stay safe and enjoy.