Need code in Python 3

I need to create function, that sorting dictionary

I have dictionary, for example dict:

{'1.txt': ['4.txt', '3.txt'], '2.txt': ['3.txt', '4.txt'], '3.txt': ['8.txt', '7.txt','9.txt']}

I need to sort his values like this: {'1.txt': ['3.txt', '4.txt'], '2.txt': ['3.txt', '4.txt'], '3.txt': ['7.txt', '8.txt','9.txt']}