I know how to retrieve a file with a specified name like this:
HttpGet httpGet = new HttpGet(siteUrl +
"_api/web/GetFolderByServerRelativeUrl('Shared%20Documents/Working%20Files/FolderName')/Files('"
+workbookName+"')/$value");
but is there a way to retrieve it without the name? maybe by index? Ive checked the documentation on https://learn.microsoft.com/en-us/sharepoint/dev/sp-add-ins/working-with-folders-and-files-with-rest but saw no other examples on how else to retrieve files