Hi. You did not enter the line of the sonnet the question refers to. This makes it impossible for it to be answered. However, when searching for your question on the internet, I was able to find another question exactly like yours, which showed the line "Rough winds from shake the darling buds of May." If that's the case for you, I hope the answer below will help you.
This line has five iambs and this can be seen because it has five pairs formed by an unstressed syllable followed by a stressed syllable.
The iamb is a set of unstressed syllables and stressed syllables. Stressed syllables are the longest syllables and have the strongest sound. If you read the line of the sonnet aloud, you can get a pattern of 10 syllables, in which pairs of an unstressed syllable and a stressed syllable form. Five pairs are formed, so the line has five iambs.
