Hello Matt,
There isn't a way to export them in the UI but it can be done with a public API call.
https://developer.mypurecloud.com/developer-tools/#/api-explorer
Just log into your org at that link and navigate to:
> Telephony Providers Edge
> Providers
> GET Get a listing of DIDs
This will return a JSON query and you will have to filter out the DIDs.
Thanks,
Chad