Hey there @emescioglu, thanks for writing! I suspect you are using an old version of QIIME 2, since we renamed that flag back in August.
2018.6
2018.8
2018.11
So, as you can see, the docs are slightly different depending on the version of QIIME 2 you are using.
If you would like to view the docs that match the version of QIIME 2 you are using, please specify the version in the dropdown in the upper left of the page, otherwise, I recommend you update to the latest QIIME 2! As an aside, all of the user docs are built and tested using the version of QIIME 2 they are written against, so that you can rest assured that, for the given version of QIIME 2, the commands listed should run as expected. Thanks!