What do I do after posting 3 Day Notice to Pay or Quit?

I inherited a small commercial property in CA and am a newbie at this, please forgive me for any mistakes.
A couple of months ago, a commercial tenant wrote me an email and mentioned that they would be selling the business and moving out of the country. After a few unsuccessful attempts at selling, they wrote me an email mid-December stating that if they could not sell the business by the last week of December, they were going to leave the country and would not have enough time to properly vacate/clean up (the store has everything in it still). Now they have not paid the rent after giving them additional days on top of the grace-period as stated in the Lease. I decided to post a 3 Day Notice to Pay or Quit on the door of their business and will be mailing one to the property address along with the "home" address provided in the Lease.
If they do not pay and/or respond within 3 days, do I have the right to enter the property, clean it out, and begin to look for a new tenant? Do I file anything?
I have also confirmed that the tenant is out of the country and have tried to communicate with them to get an answer as to what their plan is, as they have a year left on the Lease.