Use the compounding formula:
A(t) = A0·(1 + rate/n)nt
where:
A(t) = the amount (balance) you have after t years
A0 = the starting amount = $4200
rate = the interest rate expressed as a decimal = 0.02
n = the number of compoundings per year = monthly = 12
t = years = 34
Plug in the numbers and use your calculator to get the answer.