How to send notification to opportunity owner on some condition in Salesforce?

Hi Deepak,

You can achieve this functionality by having time dependent action in process builder or time dependent workflow action.

The criteria for step will be if opportunity status is InActive and Last Activity change date field is updated then trigger a time dependent action in process builder by having a criteria like after 2 days of Last Activity Date.

Try to create one custom field. I have tried this by creating one custom field called Last Activity Date and i am able to select that field from the drop down.

Thanks