I’m not sure if your question is directed at me specifically, or if you’re asking about any poet’s poems in general, but if you’re writing poems in free verse, then there’s no format necessary.
If you’re writing a specific type of poem, such as a sonnet or haiku or sestina, then you’d need to know the format, because you might need to have a certain number of syllables or words or patterns. You can easily find out guidelines to those types of poems on Google.