garage being used as storage

[Tom Server]

So I'm in the process of purchasing my first triplex. The property currently had 3 tenants paying under marker value.. I'm still cash flowing. My questions is 2 of the units contracts are up on Feb 2024 and the other is up sept 2024.  All tenants have been there over 5 years.  I seen the lease agreement and I don't see anything about the 3 car garage on the property. The 3 car garage is detached and has one of the units above it. Their main electric circuit board in the garage. 

Inside the 3 car garage is all kinds of their personal storage, I don't know if its from all 3 units or from the unit above.. 

What is the best way of finding out whose stuff it is?  

How long of a time frame should give them to clean it out ? 

How do I go about charging them. ? should I assign a bay to each unit?

I also cant have it locked up cause the upstairs units electrical box is in there.. any suggestions?