Access Web App is very convenient because it uses Azure SQL Database in the back end but it has been abolished.
PowerApps is announced as a successor service. Since PowerApps requires a separate Azure agreement when using Azure SQL Database as a data source, it is difficult to migrate from Access Web App to PowerApps using only Office 365 services. Therefore, I think that it can not be called a successor service. I would like you to change the database on Azure you used with Access Web App so that it can be used by PowerApps as it is.