Passing File IDs from Power Apps to Power Automate and merging into PDF, then send an email

Hello,

I'm working on a PowerApps application that allows users to select specific files from a gallery (connected a sharepoint library), display them on a table for confirmation and then merge into a pdf to send to themselves. The process involves passing the IDs of the selected files from PowerApps to Power Automate, filtering the files based on these IDs, extracting the file content and merging them into a PDF.

I'm struggling with passing the IDs from Power Apps to automate. The flow reads the entire library (200+ items) instead of just the selected. 

The configuration for my PowerApp button to call the flow is:

MergePDF.Run(Concat(SelectedItems, (ID),",");

Notify("Export process started. You will receive an email once complete.", NotificationType.Success, 3000)).

   

Please help ASAP!!