Transpose issue

[novice92]

Hi

As my username may suggest I am pretty new to both Excel and this forum , this is my first post in fact. I have attached the file containing parts of my data ( it apparently exceeded maximum file size) as it may make it easier to understand what im trying to do.

I am trying to transpose the data in the "Length" column so it ends up paired with correct ID in rows as can be seen on the right hand side. I have not been able to find any other way of doing this except manually selecting the "Length" data belonging to one ID and then copy - transpose. Surely I am overlooking some less time consuming way of transposing than to manually copy paste thousands of times?

I would be extremely grateful for any suggestions of less time consuming ways to transpose the data.