RSA: How do I decrypt this? Sorry if this is asked a lot, I just don't know if there's a specific word for it.

I'm at uni and have a codebreaking exam in a few days, I don't have to do well in it but I want to do as well as I can, but this is really making me struggle. 

Here is my work so far, everything's going alright:


  


Obviously when I try to do the bottom part, any calculator I use says it's invalid or infinite, I understand it's a crazy big number, but I have no idea how to work it out otherwise.
If you want to do it with hand calculator, you can use exponentiation by squaring, and compute the remainder after each multiplication. (instead of first computing huge powers and only then taking the remainder)