Import data that's stored somewhere else into your model-drvien app using the import feature in Power Apps.
Every table has required columns that must exist in your input file. It's recommended that you download an Excel template, add your data, and then import the file to your app. The template saves time and effort. Don't add or modify columns in the template to avoid issues during the import.
Note:
Step 1: Download an Excel template
To avoid mapping issue, it's recommended that you use an Excel template that you can download from your app. Once the template is downloaded add your data and then import the file back to your app. Remember don't add or modify columns in the template to avoid issues during the import process.
Step 2: Import your data
Use the template that you downloaded in the previous step (modified with your data) and import the file to your app.
Reference:
https://docs.microsoft.com/en-us/powerapps/user/import-data