backup.gs

function Backup() {
  let sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("transaction");
  const backupSheetUrl = 'https://docs.google.com/spreadsheets/d/1SSHx4RiytJoV3X6EgtSb0bNow1YIt8txfrllEIZF9Pc/edit';
  
  // `Sheet2` is where we want to paste our Original Data
  let backupSheet = SpreadsheetApp.openByUrl(backupSheetUrl).getSheetByName("Sheet2");
  let values = sheet.getDataRange().getValues();
  
  // Clear data but keep format in backupSheet
  // you can use `backupSheet.clear()` to clear both data and format
  backupSheet.clearContents();

  // paste data into Backup Sheet
  backupSheet.getRange(1,1, values.length, values[0].length).setValues(values);
}