Topic: CODING PROBLEM

I think this topic shouldn't be here, thou I didn't know where to open it, so as this is Problem Solving part I decided to open it here.

How can I code and/or uncode such thing? Which web tool can I use?

UWQYRUz87XUFAssdADAJSDASDMFShIGhyZ
BIUCBOZXdzIE1hbQgU3lzdGImh0dHA5cHggV8

thanks.