Definition: In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.
Input: Sentence: 'the green and purple umbrellas are upside down in the water next to the canoes'. Reverse all words of length '6' in the given sentence.

the green and elprup umbrellas are edispu down in the water next to the seonac