How do I journalize this
a. Unexpired insurance at December 31, $2,700.

Assuming you used the expense method of accounting the entry would be:

dr. prepaid insurance 2700
Cr. Insurance expense 2700

But if you used the accrual no need to adjust the unexpired but the adjustment would pertain to the expired portion

Origanl entry:

dr. prepaid insurance
Cr. Cash

Adj entry

dr. insurance exp
Cr. Prepaid isnurance

This would give you the insurance expensed out for the year, and the unexpired part of your insurance.