I will guess that you mean "y = log<sub>6</sub>(x)" (that is, log-base-6 of x equals y, or log_6(x) = y).
You can use either the change-of-base formula, and plug this into your calculator, or else you can use the definition of logs, converting this to x = 6<sup>y</sup>, and working backwards.
Which method are you using? How far have you gotten? Where are you stuck?
Please be specific. Thank you.
Eliz.