I am 5"10
It is harder to find dresses and skirts when you are this tall, you really have to be really careful with measurements and such (as if you don't need to as it is in this hobby).
Some indie brands that are willing to make their dresses longer for you if you ask, otherwise I recommend looking for underskirts that will lengthen your dresses. Sadly, there are going to be brands you need to avoid, especially Angelic Pretty does not exactly cater to taller lolitas.
I recommend looking at
this topic on cgl, and also feel free to ask questions there as well but read the already available replies. There are a lot of great posts there, and it's also good if you want to get into other j-fashion than lolita