I thought this would help you to convert for single/specific file by ID from MS Excel file to GS and return the new sheet Id converted to Google sheet.
function testConvertExcelToGS(fileId = '*your file id*') {
var file = DriveApp.getFileById(fileId);
Logger.log('file id %s',file.getName());
let blob = file.getBlob();
Logger.log('bolb file: %s:',blob);
let config = {
title: file.getName(),
parents: [{id:'*The folder id you want to copy/create GS version of MS Excel*'}],
mimeType: MimeType.GOOGLE_SHEETS,
convert: true
};
Logger.log('config title: %s', config.title);
let spreadsheet = Drive.Files.insert(config, blob);
Logger.log('The new spread sheet id: %s',spreadsheet.id);
return spreadsheet.id;
}