A finite geomeric sequence has t1 = 0.1024 and t2 = 0.256. How many terms does sequence have, if its middle term has the value 156.25?

How do I do this question? I am little bit confused!

t1 = 0.1024 t2 = 0.256

r=t2 /t1 = 2.5

t1r^n-1 = 156.25

(0.1024)(2.5 ) ^n-1= 156.25

(0.1024)(2.5 ) ^n-1= 156.25/ (0.1024)

(2.5 ) ^n-1= 1525.878906

how do I get n by itself??? am I doing this wrong? thanks for your help! :)