Flash Fill is on by default and automatically fills your data when it senses a pattern. However, if it’s not working as expected, here’s how you can check if Flash Fill is turned on.
Click File > Options.
Click Advanced and make sure the Automatically Flash Fill box is checked.
Click OK, and restart your workbook.
Start Flash Fill manually
If Flash Fill is turned on but doesn’t start automatically when you type data that matches a pattern, you can try starting it manually by clicking Data > Flash Fill, or by pressing Ctrl+E.