Need help on MongoDB Update Snap

I have inserted salesforce data into one of the Mongo database collections using MongoDB Insert. However, I will have to update the salesforce data I just inserted. How do I accomplish this by using MongoDB Update? I read through the Snap documentation, however, not helpful in this case.

Essentially, I will have to Salesforce Read LastModifiedDate and see if it is greater than today. If an account has updates, I need to locate this update and update this account in MongoDB accordingly.

Please help in this perspective! Thanks a million!