Please refer: https://docs.mendix.com/developerportal/operate/restore-backup
Nirmalkumars answer is on restoring the data.
If you are using version control and want to revert to a previously committed version of your model, you can do a reverse merge: https://docs.mendix.com/refguide7/using-version-control-in-the-dm#7-2-3-reverse-merging