To install the latest PnP core, go to your Project References > Manage nuget packages.
Download the SharePointPnPCoreOnline component. Its version should be 2.20.1711 or higher (i.e Nov 2017 or higher).You also need to add the statement using OfficeDevPnP.Core.Sites; in your class.
To create a Modern team site, you can use the below code:
CommunicationSiteCollectionCreationInformation communicationSite = new CommunicationSiteCollectionCreationInformation { Title = "Demo Communication Site", Url = "https://gowtham.sharepoint.com/sites/Demo", SiteDesign = CommunicationSiteDesign.Topic, Description = "Demo modern communication site description", Owner = "gowtham@tenant.onmicrosoft.com" AllowFileSharingForGuestUsers = true }; var createCommSite = await context.CreateSiteAsync(communicationSite);